PhD Thesis in music acoustics
FROM AIR TO MUSICAcoustical, Physiological and Perceptual Aspects of Reed Wind Instrument Playing and Vocal-Ventricular Fold Phonationby©1998An ancestral and recurrent dream of humankind is that of flying.
In my ordinary flying dreams,
whenever I inhale, I start levitating in the space;
when I exhale, I immediately return to the firm ground.
Playing a wind instrument may follow the same simple, supernatural rule:
in blowing, one donates life and sound to other beings, and gains the Earth;
in inspiring, one must incorporate spirits and angels.
Contents:Thesis front cover
AbstractThesis back cover (spectrogram of "oh, Susanah" during overtone singing in VVM phonation- see Paper VI)
2.List of abbreviations and conventions
6.Playing a reed woodwind
7.Basic ideas and methods
8.Summaries and comments on individual papers
9.Music continues; a list of possible future investigations
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©1998 by Leonardo Fuks
terça-feira, 25 de dezembro de 2012
This thesis presents an interdisciplinary research on reed woodwind instruments and human voice, focusing on acoustical, physiological and perceptual aspects of sound generation.
The wind instruments studies concentrate on breathing and blowing under realistic conditions and provide a deeper insight on required aerodynamical input parameters. The variation of blowing pressure with loudness and fundamental frequency was measured in professional players of oboe, bassoon, clarinet, and alto saxophone and was found to be quite systematic, though differing between the instruments. Airflow for sustained tones was measured by indirect spirometry, together with blowing pressure and sound pressure level, using extreme reeds, one soft and one hard. Recordings were made in an ordinary room as well as in a calibrated reverberant chamber. Also, tones with an intense vibrato were analysed for the oboe, the saxophone and the bassoon. The results revealed wide variations in blowing pressure, suggesting that a rhythmic modulation of the contraction of expiratory muscles was a main factor, and relatively small variation in fundamental frequency. The players’ perception of self-produced static lung pressures typically used in performances was analysed in a psychophysical experiment, that revealed a quasi-linear relationship between perceived and produced pressures. The respiratory movements during playing were measured by a non-invasive technique, respiratory inductive pletysmography, which offered acceptably reliable data. The results revealed significant participation of the rib cage in all players and also of the abdominal wall in several players. Also, the impact of the continuous changes of O2 and CO2 gases in the pulmonary air exhaled during performance on the fundamental frequency was predicted from theory and compared with experimental data. The effect, smaller than that of temperature variation, still would represent a factor of potential relevance to wind instrument intonation. In addition, the sound production characteristics of a particular type of phonation, perceptually judged as similar to that used in Tibetan chant, were studied by high-speed imaging. Also, it was examined using acoustical and physiological methods. The results revealed a synchronised co-oscillation of the vocal and ventricular folds, which yields a lowering of fundamental frequency due to multiplication of the vocal fold period.
Keywords: blowing pressures, reed woodwinds, oboe, clarinet, saxophone, bassoon, music performance, respiratory inductive plethysmography, perception of blowing pressure, intonation, aerodynamics, Tibetan chant, ventricular folds, respiratory behaviour, airflow, vibrato, music acoustics, physiology of music.
©1998 by Leonardo Fuks
1. Included papers
The present dissertation comprises a summary and the following papers, listed in systematic order. Click to read the abstract of each one. The available papers are undelined, just click to load them.
Paper I Leonardo Fuks & Johan Sundberg (1996): "Blowing pressures in reed woodwind instruments", KTH TMH-QPSR 3/1996, 41-57, Stockholm, to appear in a revised and modified version as "Blowing pressures in bassoon, clarinet, oboe and saxophone", in press for Acustica/acta acustica.
Paper II Leonardo Fuks (1998): "Aerodynamic input parameters and sounding properties in naturally blown reed woodwinds", KTH TMH-QPSR 4/1998, 1-11, Stockholm
Paper IIIa Leonardo Fuks (1996): "Prediction of pitch effects from measured CO2 content variations in wind instrument playing", KTH TMH-QPSR 4/1996, 37-43, Stockholm
Paper IIIb Leonardo Fuks (1997): "Prediction and measurements of exhaled air effects in the pitch of wind instruments", Proceedings of the Institute of Acoustics, ISMA'97 Conference, Edinburgh, Vol. 19: Part 5 (1997), Book 2, 373-378
Paper IV Leonardo Fuks & Johan Sundberg (1998): "Respiratory inductive plethysmography measurements on professional reed woodwind instrument players", KTH TMH-QPSR 1-2/1998, 19-42, to appear in a revised and modified version as "Using Respiratory Inductive Plethysmography for Monitoring Professional Reed Instrument Performance"; in press for Medical Problems of Performing Artists, March 1999
Paper V Leonardo Fuks (1998): "Assessment of blowing pressure perception in reed wind instrument players", KTH TMH-QPSR 3/1998, 35-48, Stockholm, submitted for publication
Paper VI Leonardo Fuks, Britta Hammarberg & Johan Sundberg (1998): "A self-sustained vocal-ventricular phonation mode: acoustical, aerodynamic and glottographic evidences", KTH TMH-QPSR 3/1998, 49-59, Stockholm
The blowing pressures during wind instruments playing have not been systematically measured in previous research, leaving the dependencies of pitch and dynamic level as open questions. In the present investigation, we recorded blowing pressures in the mouth cavity of two professional players of each of four reed woodwinds (Bb clarinet, alto saxophone, oboe, bassoon). The players performed three different tasks: (1) a series of isolated tones at four dynamic levels, (2) the same series with a crescendo-diminuendo tones and (3) ascending-descending musical arpeggio played legato at different dynamic levels (pp, mp, mf, ff). The results show that, within instruments, the players' pressures exhibit similar dependencies of pitch and dynamic levels. Between instruments, clear differences were found with regard to the dependence on pitch.
Input aerodynamic parameters in reed woodwinds - oboe, alto saxophone, bassoon and clarinet - were measured when professionals played different pitches at three dynamic levels. Two reeds were used, one rated as a hard and another as a soft reed. The tasks consisted of playing long sustained tones with and without vibrato. Audio and blowing pressure signals were recorded. Lung volume variations were indirectly measured by a spirometric procedure, which also showed the average air consumption, i.e. the mean airflow. The tones were played in a laboratory room and also in a calibrated reverberant chamber allowing estimation of radiated sound power. Average values for flow resistance, aerodynamical power and mechanical efficiency were computed. Airflow and input power varied con-siderably between instruments and between the two reed types, but generally increased with sound level. For vibrato tones produced on oboe, bassoon and saxophone, wide pressure oscillations were observed, on average 10 cm H2O for the oboe and bassoon, and reaching values of 20 cm H2O in some cases. Possible origins of these pressure variations are discussed.
The effect of carbon dioxide (CO2) exhaled by wind instrument players on the resulting pitch is investigated. A theoretical-numerical approach is applied to determine the dependence of sound velocity on the percentage of CO2 contained in the air. Realistic performance data were obtained from experiments in which a professional musician played a clarinet and an oboe, while the CO2 content of exhaled air was recorded together with the audio signal. By calculating the impact of the variation of CO2 and O2 contents on sound velocity, considerable effects on the fundamental frequency of the tones produced are predicted.
The natural resonance frequencies of wind instruments are dependent on the geometry of the air
column, the dimensions and design of reed/mouthpiece, the placement and size of toneholes and the sound speed in
the gas inside the instrument. Also, this gas continuously changes in composition with respect to the content of
carbon dioxide (CO2) and oxygen gas (O2) due to the player's metabolic activity. These changes should affect the
fundamental frequency to some extent. This frequency is also a function of the embouchure configuration and the
highly varying blowing pressures . The purpose of the present study was to provide an experimental and theoretical
basis for analysis and measurement of the impact of the gas changes in the sounding pitch.
Typical atmospheric air contains a concentration of CO2 ranging between 0.03% and 0.06%, while O2 is found at a percentage of approximately 20.9 %, regardless of local altitude. These are the gases whose percentages change between inhaled and exhaled air. In addition, there is metabolic production of water, which is expelled as saturated vapour. It is also important to note that the respiratory airways comprise a volume defined between the air inlet and the first pulmonary structures, called anatomical dead space, in which the air practically does not change in composition from the ambient values. The anatomical dead space is in average ca. 150 ml. Variations in exhaled CO2 during performance of a solo work with the oboe and sustained tones with the clarinet have been previously documented. The results showed that in wind instrument playing, the CO2 contents in the pulmonary air may vary considerably with time, roughly from 2.5% just after a deep breath up to 8.5% after a long playing period of ca one minute. The O2 contents in the alveolar gas, thus the air to be exhaled, are reported to achieve a minimum value of 14%.
During playing wind instruments such as the oboe and the clarinet, the content of CO2 in the expired air varies between the ambient level and up to 8.5% in extremely long phrases, while for the O2 it may vary from the ambient 21% down to 12%, or even less. The increase in CO2 tends to decrease the pitch and the fall in O2 tends to increase pitch. Even then, due to differences in gas properties and the rate with which the gases vary, the total effect is that of pitch decrease. This effect may account for a fall in fundamental frequency of the tones by more than 20 cents. Although we could presume that the pitch effects induced by gas variation are compensated for by the player by means of varying embouchure, blowing pressure and other playing characteristics, this effect still seems a relevant factor in wind instrument playing.
Respiratory movements and lung volume variations during natural performance of wind instrument playing have been scarcely documented in the literature, but may provide a deeper insight into performance techniques, players' physiological characteristics as well as into the physics of the instruments. Using Respiratory Inductive Plethysmography (RIP) respiratory movements of eight professional players (oboe, clarinet, alto-saxophone, bassoon) were measured during playing of exercises and orchestral solo voices. Calibration of the relative contribution of abdominal wall and rib cage regions was achieved from isovolume manoeuvres. Pneumotachometry was applied for absolute calibration of the RIP. Flow through a standard aerodynamic resistance at constant pressure was used for assessing the method of measurement under dynamic conditions. Different possible artifacts are described and discussed. The method yielded linear and accurate results, provided that significant body movement is absent, appeared to be non-disturbing to the musicians, accurate and robust. Depending on instrument and piece the players initiated the breath groups at 55% - 87% and terminated them between 14% - 52% of their vital capacity. Unlike what has been found for singers, the players generally showed simultaneous and in many cases equally important contributions from rib cage and abdominal wall during playing. In extreme cases, inhalations were achieved in approximately 300 ms and reasonably synchronised with the RIP signals.
Perception of blowing pressures in eight reed instrument players was assessed by means of a psychophysical production method. The aim of the study was to investigate how the players judge mouth pressures independently from playing conditions, i.e., without embouchure effort, reed vibration, airflow or auditory feedback. Reference pressures were established by relaxation at three lung volume levels ranging between just above functional residual capacity (FRC) to nearly full lungs. Successive doubling estimates were employed to assess the relationship between pulmonary pressure - a physical variable, and perceived pressure - a psychophysical variable. Regression analysis was applied to the data under four different models - linear, logarithmic, exponential and power functions. Generally, the linear model was the one that presented a highest correlation with the experimental data (r2=0.943), while the logarithmical model (Fechner Law) corresponded to a lowest correlation (r2= 0.869). The power function exponents (Stevens Law, r2=0.924) varied considerably among subjects, with a global average of 0.94, and among the three increasing lung volume levels, 0.79, 0.92 and 1.13, respectively. The method provided consistent data from the subjects and the results provided information about this rarely studied modality.
This investigation describes various characteristics of a particular phonation mode, vocal-ventricular mode (VVM), as produced by a healthy, musically-trained subject. This phonation mode was judged as perceptually identical to that used in the Tibetan chant tradition. VVM covered a range close to an octave, starting at about 50 Hz. High-speed glottography revealed that the ventricular folds oscillated at half the frequency of the vocal folds thus yielding a frequency of f0/2. Phonation at f0/3 was also possible. Presumably, aerodynamic forces produced by the glottal flow pulses sustained the vibrations of the ventricular folds. Complementary aspects of this type of phonation were compared to phonation in modal and pulse registers by acoustical analysis of the audio signal, by inverse filtering of the flow signal and by electroglottography (EGG). In addition, oesophageal pressures were measured. These analyses revealed that every second flow pulse was attenuated because of the ventricular fold vibrations and that the laryngeal contact area alternated between two minimum values. The spectra of VVM sounds contained clear harmonic partials up to about 4 kHz. Oesophageal pressure tended to change when phonation switched between VVM and modal phonation. Examples of periodic pulse register, another case of voice period multiplication, produced patterns of EGG waveform differing from those of VVM. The possibilities of using VVM in contemporary music, whether in a purely vocal form or during to wind instrument playing, are discussed.
©1998 by Leonardo Fuks
2. List of Abbreviations and Conventions
The papers will be henceforth referred to by their Roman numerals.
Figures and Tables will be referred to by the same way as they appear in their respective papers.
Note name convention: the real note names, rather than the transposed ones are adopted throughout the thesis.
For example, in the alto saxophone, A4 stands for the standard A 440 Hz, rather than C4 as it would sound from a score.
D Pmouth amplitude of mouth pressure variations during vibrato
AW abdominal wall
c velocity of sound
ERV expiratory reserve volume
FRC functional residual capacity
IC inspiratory capacity
Irev sound intensity as estimated in the reverberant chamber
IVM isovolume manoeuvre
jnd just noticeable difference
p0 , Pmouth or Pm pressure in the mouth, blowing pressure
PFE power function exponent
RC rib cage
REL resting end-expiratory level
RIP respiratory inductive pletysmography
RV residual volume
SPL sound pressure level
TLC total lung capacity
Tr reverberation time
airflow through the reed/mouthpiece
VC vital capacity
Vt tidal volume
VVM vocal-ventricular (phonation) mode
©1998 by Leonardo Fuks
Respiration and breathing are keywords in this thesis, since they play a central role in wind instrument playing as well as in voice production. In wind instrument playing and in singing the performer shares the vital metabolic air with the sound-producing organ. In a more general perspective, respiratory pauses and sometimes even respiratory sounds contribute significantly to music performance, also in the case of some non-wind instruments. For instance, in the playing of bowed string instruments, western classical performers frequently employ the sounds and gestures of respiration to enhance expressiveness and also to mark musical phrases. Thus, breathing and the associated pauses serve as structural elements in musical performance, often possessing a significant esthetical content.
This study comprises a suite of papers conceived with the intention to examine the theme under an interdisciplinary perspective, including musical, acoustical, perceptual and physiological aspects. It is concentrated on the mechanical-reed woodwinds, henceforth reed woodwinds, which comprise the oboe, clarinet, saxophone and bassoon. This interdisciplinary approach is justified by the assumption that it is not possible to fully understand the process of playing a wind instrument if any of these aspects is overlooked in the analysis. Figure 1 shows a schematic representation of the breathing behaviour in wind instrument playing.
Figure 1. Illustration, in the form of a trefoil diagram, of the phenomenon of breathing behaviour in wind instrument playing. As shown, breathing needs to accommodate demands originating from three main systems: performer, instrument and musical work.
As schematically illustrated in Figure 1, breathing behaviour in wind instrument playing is influenced by a great number of different factors, each raising demands on the player's performance. The structural organisation of the music imposes certain requirements regarding tempo, phrase length, dynamic variation, and the musical role in the ensemble. The performing artist has to accommodate these demands within the constraints and potentials of his own physiological system, including respiratory, perceptual, and proprioceptual capabilities. The instrument consumes air, provided by the player’s metabolic system. It consumes air to an extent that depends on many factors, such as the desired acoustical output, the technique of playing, and the responsiveness of the instrument. The task of the musician is to harmonise all these factors so as to reach a satisfactory artistic end result. Many of these factors have been neglected in previous investigation of wind instruments. Conversely, some research in the area of respiration may profit from improved information about breathing characteristics of wind instrumentalists. Likewise, the understanding of the function of wind instruments, as well as of the musical work and its performance, may gain from information about the physiology of the player. In addition, the knowledge gathered and produced in this thesis may have applications in the development of new playing techniques, the designing and improving of instruments, in compositional work, as well as in the development of computer algorithms for artificial instruments. From a wider perspective, the thesis can be regarded as a meeting point of several disciplines, such as musical acoustics, instrument making, music theory, physiology, ergonomics, and instrumental practice.
©1998 by Leonardo Fuks
4. Previous work
4a Physiological Aspects of Music Performance
Early interest in how players behave in order to operate wind instruments dates at least from the last century (Stone, 1874; Barton & Laws, 1902). Most of those studies were produced by physiologists who were mainly interested in the supposedly extreme levels of effort required, their physiological effects on circulation and respiration and on possible association to respiratory diseases (Frucht, 1937; Roos, 1936, 1938, 1940; Faulkner & Sharpey-Schafer, 1959; Singer, 1960; Akgun & Ozgonul, 1967; Watson, 1972; Gibson, 1979; Schorr-Lesnick et al., 1985; Gilbert, 1998). Part of this literature refers to pulmonary emphysema, a chronic pulmonary disease (Becker, 1911; Hävermark & Lundgren, 1957; Rejsek et al.; 1961). In this disease, there is an abnormal enlargement of the air spaces distal to the terminal bronchioles, accompanied by destruction of their walls (Snider, 1994). Yet, the claim that the playing of wind instrument might predispose to the development of pulmonary emphysema has never been confirmed (Bouhuys, 1964; Lucia, 1994). Rather, emphysema has been proved to be connected to smoking habits, to chronical respiratory disease and to genetically-related disposition (Snider, 1994). On the other hand, patients with respiratory problems who have music as an occupation are more likely to experience symptoms triggered by the demands imposed by performance. Similarly, wind players will tend to notice more clearly the physiological modifications associated with aging.
Arend Bouhuys probably contributed most importantly to the present knowledge on physiology of wind instrument playing. He studied pressure, airflow, sound power, efficiency, CO2 variations, heart rates, and other aspects (Bouhuys, 1964, 1965, 1968). Using a pneumograph he assessed qualitatively lung volume variations and also discussed some respiratory techniques, such as circular breathing (Bouhuys, 1964).
Based on the fact that blowing pressure in the observed brass instruments presented wider ranges than in woodwinds, Bouhuys hypothesised that mouth pressure control would be more important for those instruments than in any other type of winds. It must be borne in mind, however, that in brass instruments, where the lips serve as the oscillating reeds, the lip tension control is as important as the expiratory pressure. In woodwind, the embouchure, i. e. the link between the player’s mouth and the instrument (see below), is also very relevant, although it does not affect the pitch to the same critical extent as in brass instruments.
Other contributions to the physiology of wind instrument playing were given by Navrátil & Rejsek (1968), Vivona (1968), Benade (1986), among others.
4b Music Acoustics
Wind instruments have been intensely investigated in the domain of music acoustics. From the pioneering contributions of Weber (ca. 1830, as quoted by Bouasse, 1929) and Helmholtz (1863), followed by the important work of Bouasse (1929), the physics of wind instruments has attracted the attention of several generations of investigators.
With regard to reed woodwinds, particularly significant contributions were offered by Meyer (1961), Backus (1961, 1963a, 1963b, 1977), Benade (1968, 1976, 1986, 1988), Nederveen (1969), Worman (1971), Bak (1978), Plitnik & Strong (1979), Thompson (1979), Stewart & Strong (1980), Schumacher (1981), McIntyre et al. (1983), Pawlosky & Zoltowsky (1985, 1987), Gilbert (1986, 1989, 1991), Meynial (1987), Sommerfeldt & Strong (1988), Gibiat (1990), Hirschberg et al. (1990), Keefe (1990), Idogawa et al. (1993), and others.
A majority of the studies of reed instruments concern the acoustics of the clarinet, a quasi-cylindrical tube resonator excited by a simple-reed oscillator. The large concentration of studies on this instrument is probably due to the fact that the instrument possesses characteristics that are favourable from the point of view of experimental research. For example, the amplitude of vibration may be relatively small and the reed does not necessarily beat against the mouthpiece. This and the quasi-constant cross-sectional area of the tube resonator reduce complexity, particularly as compared to double reeds attached to conical tubes. In addition, the clarinet is a widespread and reasonably low-priced instrument, homogeneous in terms of design and used in many types of ensembles and styles.
The combined theoretical and experimental knowledge provided by the above-mentioned and other studies, permits simulation and prediction of instrument behaviour, at least under specific circumstances. However, many problems need still to be solved before the full system can be exhaustively described. The instruments are geometrically complex with a multitude of tonehole configurations, the reeds are neither standard, nor homogeneous, and the player’s behaviour cannot be assumed to be constant and absolutely reproducible. In addition, music requires quite fast and complex changes of the output sound. All this causes difficulties in defining parameters and initial conditions of a system of equations intended to describe, at least hypothetically, the phenomena involved. Fletcher & Rossing (1998) point out that an accurate prediction of the airflow through a wind instrument, that takes into account the effect of viscosity, necessarily requires the solution of the Navier-Stokes equations (e.g. see Yih, 1969). These are non-linear and would demand numerical methods for their solution, once the system is suitably defined.
4c Musical Pedagogy
Many pedagogical text-books for wind instruments, sometimes called "methods", often considers techniques for respiration and breathing for sound production (Quantz, 1752; Rockstro, 1890; Palmer, 1952; Rothwell, 1953, 1976; Thurston, 1956; Spencer, 1958; Stein, 1958; Sprenkle & Ledet, 1961; Bonade, 1962; Teal, 1963; Timm, 1964; Putnik, 1970; Goossens, 1977; Weait, 1979; Mazzeo, 1981; Mauk, 1986; Rehfeldt, 1994). In some cases, these sections review some basic anatomy of the respiratory apparatus, sometimes complemented by descriptions of the inspiratory and expiratory muscles, recommendations on posture during playing and on optimum inhalation strategy and instructions on how to achieve "support" and "use the diaphragm". Unfortunately, these two latter terms seem vague and used in diverging meanings among different authors. In addition, differing meanings of the same term are often used in different fields. Obviously, this lack of consensus regarding the meaning of terms will cause misunderstandings and confusion among students and colleagues.
Occasionally there is a marked discrepancy between the contents found in musical text-books and the current knowledge in respiratory physiology and mechanics; sometimes totally neglected are the great advances, achieved particularly after the end of WWII (see e.g., Rahn, 1946; Agostoni 1964, 1965, 1967; Wade, 1954; Konno and Mead, 1967, 1968; for a broad and detailed account of respiration, see Roussos, 1995). This obviously hampers interdisciplinary communication.
A professional brass instrument player and teacher, Arnold Jacobs (1915-1998), in particular, has paid major attention to respiratory aspects. Jacobs was probably the most influential wind instrument teacher in the USA and other countries, particularly among brass players. His pedagogical activities were exclusively oral, through private lessons and workshops (Stewart, 1987; Frederiksen, 1996). In his lessons, Jacobs used an ensemble of devices, developed for respiratory clinical purposes, providing visual feedback to the students regarding pulmonary pressure, air flow and lung volume. Also, he designed or adapted some equipment aiming at stimulating respiratory function in players and at increasing the degree of consciousness and training regarding muscular control. Interestingly, Jacobs used a terminology that was more pedagogically-oriented than based on physical facts. For instance, he emphasises "flow" as a keyword for playing control, as opposed to "pressure", which he deemed a negative term. This seems to be due to the psychological effect of these words. Different terms may tend to trigger different behaviours in players. Probably he did not overlook the fact that reed wind instruments and brass instruments are generally regarded as pressure-controlled systems (Benade & Gans, 1968; Elliot & Bowsher, 1982). There is also another reason for emphasising "flow". In brass instruments there is a wide range of combinations of mouth pressure and lip resistance that produce the same output level. If the player is able to use configurations requiring lower pressures, i.e., lower embouchure resistance and/or stiffness, the airflow should be maximised and the playing effort reduced (Nederveen, 1969). These general principles are likely to apply also to woodwind instruments, at least to some extent.
Music acoustics research would have the potential of contributing importantly to music pedagogy and performance. Definitions of terms based on scientific data should be easier to accept than definitions derived from experts’ introspection. Likewise, realistic ideas of anatomy and physiology have a great potential to gain wide acceptance, thus promoting interdisciplinary exchange.
©1998 by Leonardo Fuks
5. Instruments analysed
This investigation was focused on reed woodwind instruments and on voice, the latter with respect to a particular effect of vocal-ventricular phonation. Limiting the instrumental study to four types of instruments was due to practical and methodological considerations. A practical consideration was the huge amount of experiments and data processing required to achieve some degree of depth in the analysis of a given instrument. A methodological consideration was the vast differences in the principles that regulate the sound generation in different types of wind instruments, e.g., the above-mentioned mechanical reed, free reed (harmonica, accordion), air-reed (flutes, recorders, etc.) and lip-reed (brass) instruments. These differences lead to separate playing techniques, necessitating the use of different theoretical approaches for each instrument type. Nevertheless, most of the studies and procedures in this work might be useful in future investigations of other types of wind instruments.
The idea to include the human voice in this work originated from the observation of some apparent similarities between the mechanical system of reed instruments and certain properties of the specific phonation mode studied. These similarities will be explained in greater detail below.
5a Reed woodwinds
Figure 2. Bassoon plant. Despite standard and accurate manufacturing procedures adopted by the maker, the different parts of an instrument must be mutually adjusted, so that equivalent parts are not usually interchangeable. The instruments shown incorporate the German Heckel system (Blei & Baumann, 1987).
Mechanical reed woodwinds constitute an important group of wind instruments, which in western classical tradition includes oboes, clarinets, saxophones and bassoons. In these instruments, the function of the reed is to modulate the airstream that enters the air-column of the instrument, exciting and maintaining the vibrations in the bore.
Each of the instruments are available in two or more "voices", according to pitch range: soprano oboe, oboe d’amore, English horn; soprano clarinet (in Bb and in A), Eb clarinet, basset horn, bass clarinet; soprano, alto, tenor, bass saxophones; bassoon and contra-bassoon. There are still more variants. Usually, different voices of an instrument use almost identical fingerings. There are, however, instruments designed with different key systems and tonehole configurations, particularly for the oboe and the bassoon, which may also differ in sound quality and in playability, see Figure 2.
Among the four instrument types, we selected the four most commonly used, shown in Figures 3-6. The reeds for the alto soprano and the clarinet are very similar, the first being larger in all dimensions, see Figure 7. The reeds for all four instruments are generally made of a species of bamboo, Arundo donax. Other, mainly synthetic, materials are also available. However, the bamboo is by large the most common among professional classical users. Since oboe and bassoon reeds are autonomous pieces, directly attached to the instrument bore, they will be referred to as reeds or mouthpieces. Figures 3 to 7 from Nederveen (1969).
Figure 4. Soprano clarinet
Figure 5. Bassoon
Figure 6. Alto-saxophone
Figure 7. A clarinet/saxophone mouthpiece. The reed is rigidly clamped by the ligature in one extreme. The blade is free to oscillate along the curved profile of the mouthpiece. The airflow slit is the varying opening area between the reed margins and the mouthpiece lay. Embouchure sets a different contact region between the parts, moved towards the tip, characterised by a less rigid and more damped attachment (see Figures 10a and b).
Reed woodwind instruments produce tones at pitches which are dependent on many factors: the length of the acoustical air-column inside the instrument, the shape of the instrument bore, the sound speed of the air inside the instrument, the natural vibrating frequencies of the reeds and, to some extent, the blowing pressure. Also, the so-called embouchure is highly influential. The term embouchure is somewhat vague (Porter, 1967; 1973). In this thesis it is assumed to be the constellation of forces and positions in the lips, mouth region and face that act on the instrument. A more detailed account for the effects of the embouchure is given in the end of this section.
The length of the air-column is mainly determined by the fingering applied to the instrument mechanism, which permits a large combination of open and closed tone-holes. This length can be modified by the longitudinal position of the mouthpiece, which allows fine tuning adjustment of the instrument with respect to an intonation reference. The tuning is also affected by the acoustical length of the reed, which depends on the physical reed length and shape.
The shape of the instruments' bore may be roughly approximated to a cylinder in the clarinet and to a truncated cone in the oboe, saxophone and bassoon. In simplified terms, the sound waves travelling in a cylindrical tube closed at one end, such as in an idealised clarinet, may be considered as quasi plane. The frequencies of the resonance modes approach a harmonic series containing the odd multiples of the lowest resonance. For a conical tube, the waves produced are quasi spherical, thus a series comprising all multiples of the lowest resonance frequency. In reality, those resonance modes present inharmonicities, i.e. they are not exact integer multiples of the lowest resonance (Bouasse, 1929; Benade, 1968; Gilbert, 1991).
The speed of sound propagation in the instrument is of great importance. The reason is that the reed oscillations are controlled by a vibratory regime in the bore; acoustic pulses, created by the reed’s modulation of the airstream from the mouth, travel along the bore, are reflected at the effective end point of the air-column and return back to the reed chamber. The travel time depends on the length of the bore and of the sound speed. This speed depends on the temperature, humidity and the composition of the gas inside the instrument, which thus affect the fundamental frequency of the tones, see Figure 8. The magnitude of these effects is investigated in detail in Papers IIIa and IIIb.
Figure 8. Players must adapt themselves to perform under various conditions. At low temperatures, the normal fundamental pitch of a wind instrument should decrease considerably, for example, almost a semitone at -10°C. However, as the instruments are warmed up, this deviation should be greatly reduced. Photo by Blei & Baumann (1987).
The reeds generally oscillate at frequencies that are far below their inherent frequencies, i.e. frequencies at which they would vibrate should they not be coupled to an air-column (Helmholtz, 1863; Bouasse, 1929; Benade, 1976). For instance, when the player increases the load forces in the embouchure, thus increasing the reed stiffness, the inherent frequency of the reed is raised. This increases to some extent the sounding pitch. Players continuously use this principle for fine adjustments of intonation. Also, in clarinets and saxophones the single reed is bent against the curved lay of the mouthpiece, see Figure 7. This implies an increase in load force and a shortening in the vibrating length of the reed, which raises the fundamental frequency to some degree. This affects the equivalent length of the instrument (Gilbert, 1991, and see below). "Squeak" sounds, high-pitched sounds that accidentally occur mainly in the clarinet, are explained as a consequence of an insufficient coupling of the reed to the air-column modes. In this case, the reed vibrates closer to its natural frequency, occasionally reinforced and assisted by a resonant peak of the mouth cavity and/or the instrument bore. "Squeak" sounds are sometimes used in contemporary music, often controlled by the direct contact of the teeth on the reed (Rehfeldt, 1994) and/or by skilful shaping of the vocal tract.
Apart from the embouchure’s effect on reed stiffness, it probably also adds to its effective mass. The surface of the lips that touches the reed should form a layer of tissue that participates in the oscillations. This should reduce the natural frequency of the reed, implying that the fundamental frequency should decrease somewhat. This seems to be a neglected factor in previous investigations. In a pilot experiment, we applied a thin film of plastic gum of 0.1 g on both sides of a bagpipe reed, connected to its air-column (a conical chanter), blowing at constant pressure. This caused the fundamental frequency to decrease by more than 15 cents. The bagpipe reed is located inside a cap, isolating it from the lips. This result suggests that the mass added to the reed by the lips is significant.
Blowing pressure is intimately related to airflow in reed woodwinds. Analysis of the static airflow, void of oscillation, across a reed-like device has shown characteristic relations between the two, see Figure 9 (from Fletcher and Rossing, 1998, after Wijnands & Hischberg, 1995 and Worman, 1971). They reveal that, for a given embouchure, airflow varies with pressure according to a bell shaped curve. Acoustical and aerodynamical considerations show that self sustained oscillations will only be possible on the descending side of the curve and that these oscillations can be started at a threshold pressure, i.e., approximately one third of the pressure that completely closes the reed. The pressure-flow curves are different for double reeds, such as oboes and bassoons, although similar principles apply. The differences consist of the fact that in curve III there is hysteresis, implying that an increase of the upstream pressure to a maximum will suddenly interrupt the flow, while a different behaviour occurs when going the reverse direction.
In practical terms, the static flow curves show that for a fixed embouchure the airflow and the sound power radiated by the instrument should decrease with increasing blowing pressure. Papers I and II investigate the pressure and airflow in naturally played instruments.
Figure 9. Pressure-flow curves through a static reed, i.e. without oscillations. With a blowing pressure of p0 and an internal pressure of p, flow increases from O until it reaches a maximum at A and decreases until the closure point C. For the two curves on the left, the instruments can only operate in the descending part of the bell-shaped curves. Filled line represents the typical case of the clarinet (Worman, 1971). Double reeds may behave according to one of the three curves, because of internal flow resistance. From Fletcher & Rossing (1998), after Wijnads & Hirschberg (1995).
Another important phenomenon occurring in instruments is overblowing. In reed woodwinds it refers to the situation that the reed vibration frequency is controlled by a higher oscillation mode of the air column. Overblowing is caused by a particular combination of embouchure and input parameters, sometimes assisted by a special fingering. As mentioned above, conical bores have modes at approximately integer multiples of the frequency of the lowest mode. Thus, overblowing will make the reed oscillate at higher resonance modes in the air-column. Similarly, in conical bores overblowing establish reed vibrations at frequencies which are about 3, 5, 7 etc. times the lowest mode. The overblowing phenomenon delimits the different registers of the instrument. Generally, the reed instruments use no more than three registers but under special circumstances, additional registers may occur.
The oboe, Figure 3, has a length of approximately 644 mm, including the reed, and its usual range is Bb3-G6. The first register is limited by the note C5. The second runs up to C6, and has fingerings very similar to those in the first register. The fingerings in the third register are less systematic for reasons of tuning. The double reed, consisting of two opposed, curved blades tied to a metal staple, is shown in more detail in the same figure. Of paramount importance is the design and finishing of the reed scrape, as it affects the playing properties of the reed. Usually, oboe and bassoon players make and adjust their reeds according to the instruments, the material properties, and to personal preference.
The Bb clarinet, Figure 4, has a bore measuring about 664mm and is approximately cylindrical. The instrument typically ranges between D3 and B6. Ab4 limits the first register. Because its air-column modes are odd multiples of the fundamental mode, the second register gives three times the fundamental frequency, in musical terms a duodecim or a twelfth. This register is available from A4, which uses the fingering of D3 plus the register hole. This register continues up to Bb5 (position corresponding to Eb4). From this point on, the third register follows until B6, with non-sequential fingerings as in the former registers. Only Boehm system clarinets, the most widespread, were used in our experiments.
The bassoon, Figure 5, like the oboe, consists of a conical tube with a double reed, measuring approximately 2560 mm and ranges typically between Bb1 and D5. The first register spans from Bb1 to F3. This is considerably larger than the other instruments. From F#3 up to D4, the fingerings are similar to the previous octave, with the assistance of some keys. Then, the last octave comprises fingerings that vary greatly. In our experiments, all bassoons belonged to the German (Heckel) system, see Figures 2 and 5.
The alto saxophone, Figure 6, consists of a quasi-conical bore of 1062 mm and a typical playing range between Db3 to A5. The first register reaches E4, the second register covers the range F4 to A5, and uses fingerings similar to those used in the first register. For saxophones, mostly one single system is used.
From the above, it is evident that the embouchure serves many different purposes, all controlled by the player. Figure 10b presents a tentative schematic model for how the mechanical parameters of the embouchure are distributed along the reed. The lips are pressed against the reed with a load force distributed on the surface (dFm). The tissue has a stiffness (dKm) and a mass distribution (dMm), and also attenuates the oscillations with a damping coefficient (dRm).
Figures 10a and 10b. Simplified representation of the embouchure (a) and a detail with its mechanical parameters (b) on a single reed instrument. For double reeds, obviously both blades will be in contact with the lips and the factor of the reed bending along the mouthpiece lay is not present.
The purposes of the embouchure are as follows:
- Providing an airtight seal between mouth and mouthpiece. To meet this demand, the embouchure may sometimes be adapted to the blowing pressure. For instance, a pressure increase might require increase of the lip contraction so as to prevent air leakage. This may potentially affect the reed behaviour. In the oboe and bassoon, both lips are folded over the teeth, while in the clarinet and the saxophone only the lower lip usually folds over the teeth while the upper teeth are in direct contact with the mouthpiece. In addition, the upper lip is pressing anteriorly against the upper surface of the mouthpiece and laterally against its sides. Some clarinet players fold the upper lip around the teeth too, like oboe and bassoon players. This technique, called "double-lip", is argued to ensure a more relaxed, steady and balanced embouchure.
- Controlling the degree of damping of the reed vibrations (Nederveen, 1969; Wilson & Beavers, 1974). This damping can be applied in different regions along the reed surface, enabling a wide variation of the timbral output tone and vibration modes. Also, it is used to inhibit undesired modes of reed vibrations ("squeaks" e.g., in clarinet and saxophone).
- Regulating the stiffness of the reed by means of load force. This force, applied normal to the reed surface, affects the reed deflections and, in the cases of clarinet and the saxophone, also the bending of the reed along the curved mouthpiece profile, as mentioned (Nederveen, 1969; Gilbert, 1991; Stewart & Strong, 1980; Meynal, 1987). Both factors increase fundamental frequency. Gilbert (1991) measured an increase of more than 30 cents, at a constant blowing pressure, between a relaxed and a tense embouchure in a high-pitched alto-saxophone note (E5, real note).
- Regulating the dimensions of the slit through which the air passes into the instrument (Nederveen, 1969; Wilson & Beavers, 1974; Bak, 1978). This function is also carried out by means of the application of the load force, as in c. The slit, or gap, is obviously variable due to the reed oscillations. An initial static (without pressure difference across the reed) and an average dynamic gap may be determined by optical or other methods. It can be expected that the dynamic gap will be smaller than the static, since the blowing pressure would add an aerodynamic component to the loading force by the lips (Nederveen, 1969; Bak, 1978; Gilbert, 1991).
- Adding mass to the reed. Because of the direct contact in the embouchure, the lips participate in the reed vibrations, thus increasing its inertia. This effect alone would decrease the natural frequency of the reed to some extent, thus producing a decrease in fundamental frequency, as mentioned.
- Positioning and holding the instrument relative to the player. This refers to the degree of angular freedom provided by the embouchure, affecting the posture including the positioning of the arms and, to some extent, also the fingers. It has consequences for the internal configuration of the mouth and the tongue relative to the reed. The conformation of the players' teeth and jaws are also significant to the embouchure (Porter, 1967, 1973). Also, particularly for fingerings that require the right hand just to hold the instrument (with the thumb) and the left hand to apply unbalanced forces on the instrument, the embouchure may serve to support and stabilise the instrument. One example is the fingering for Bb5 in the clarinet, which tends to force the mouthpiece against the upper lip. This might be called an ergonomical function of the embouchure.
By modulating the embouchure, usually accompanied by a modulation of the blowing pressure, it is possible to produce a gamut of sound effects and gestures, including the so-called "lip vibrato", briefly discussed in Paper II.
It must be stressed that the above descriptions refer to embouchure in reed woodwinds. In the case of brass instruments, where the lips serve as the main oscillator, such function must be added and the purposes represented by items b, c and d do not apply. Also, the embouchure in air-reed instruments, such as flute and recorder, require a different description.
In defining the embouchure, it is possible also to include factors that determine the intraoral configuration, such as the position of the jaw and tongue. The shape of the mouth cavity is frequently assumed to be relevant to the sound production (Benade, 1986; Thomas et al., 1988; Backus, 1963b).
5b Human voice: Ventricular fold phonation
Human voice might be regarded as a special case of wind instrument. The source oscillations are mainly defined by the inertial and viscoelastic properties of the vocal folds and the aerodynamic parameters of the airflow passing them, while the feedback from the air column upon the vocal fold oscillator is generally of minor significance. Yet, a particular type of voicing seems interesting from the point of view of wind instrument acoustics, viz. the one produced by some Tibetan monks and ethnic groups of Central Asia. This type of voicing is characterised by a very low fundamental frequency and a loud tone, rich in harmonics as compared to corresponding tones produced by Western bass singers (Smith et al., 1967; Barnett, 1977; Dmitriev et al., 1983; Campbell & Greated, 1987; Zemp, 1996). The underlying mechanism has not been clearly explained. This raises the question whether structures other than the vocal folds could play the role of an oscillator.
It seemed reasonable to assume that the ventricular (or false) vocal folds vibrate in such voice production. The geometrical configuration of these structures differs considerably from that of the vocal folds. As can be seen in Figure 1, Paper VI, the ventricular folds have a downward angulation. Thus, they can serve as a closing valve, preventing exhalation at high intrathoracic pressures, such as during the initiation of coughing. The vocal folds have the opposite angulation, so that they can serve the purpose of closing the airways during inhalation, such as in hiccup. According to Helmholtz (1863), the valve systems represented by the reeds in musical instruments may be classified into inwards striking "tongues", or valves (e.g. reed woodwinds), and outwards striking valves (brass instruments and voice). An interesting possibility studied in Paper VI was if they then function as an inward closing valve, i.e., similar to a woodwind reed.
©1998 by Leonardo Fuks
6.Playing a reed woodwind
The skill to play an instrument is, as a rule, transmitted from master to apprentice, frequently with the help of "methods" and "études", see Figure 11. These serve as pedagogical complement to the objective study of accomplished works. Sometimes, such as in the cases of the Études for piano by Chopin or for guitar by Villa-Lobos, exercise pieces reach such a high level of musical quality that they become autonomous pieces of music.
In general, the pedagogical material is expected to offer repetitive drills and playing challenges. It is presented to the student in a suitable order and sequence of complexity so as to promote the gradual development of the student's playing technique. Also, students tend to imitate the playing characteristics of their teachers. This is often considered desirable. Very seldom a professional-level classical player is self-taught, while this may occur often in other musical contexts.
In our Western culture, the education in classical music performance belongs to a rather well-established international tradition which, however, allows for some regional/national characteristics. During this process of observation, learning and training, players often develop a strong feeling of identification with musicians with whom they share playing characteristics of their "school". Also, they often have a tendency to reject "schools" representing other stylistic and technical practices.
However the differences in playing technique between different schools seem somewhat exaggerated. A given instrument requires a certain basic behaviour on the part of the player. In addition, the instruments seem to become more and more standardised and a small number of instrument makers dominate the professional market. Also, globalisation in the recording industry and an international job market contribute to reduce the effects of nationality and "schools". As a consequence, the use of professional classical players as subjects in performance experiments tends to be geographically and culturally independent.
Apart from embouchure that has been already mentioned, posture and respiratory movements are regarded as crucial bodily aspects of performance in wind instrument along with the fingering technique. Interestingly, the latter would seem to the layman as the prime factor of playing.
Body posture is part of the performer's visual communication and can be at least partially assessed by the eyes of an experienced instructor, see Figure 11. Respiratory movements, by contrast, are much subtler and often not easy to observe by eye. In addition, posture and respiratory movements are intimately related. For instance, a maximal inhalation often requires changes of posture; a fixed expanded chest posture entails severe exhalatory constraints. A non-invasive respiratory measurement technique, respiratory inductive plethysmography, RIP, was used in Paper IV for objectively monitoring and recording of respiratory movements in performance. It measures variations in cross-sectional area for the estimation of internal thoracic volume changes. Therefore, postural changes that are independent of lung volume variations were expected to generate artefacts. This issue is examined in detail in Paper IV. We believe that this method may be useful for pedagogical and clinical purposes, as it allows monitoring of respiratory movements during musical performance.
Figure 11. Clarinet Lesson. The master usually guides the pupil in every detail of performance, transmitting traditional techniques and esthetical values. The body posture and embouchure shown suggest that the picture was taken at the instant of a quick inhalation. Photo by Blei & Baumann (1987).
A player must resort to many different techniques in realising musical ideas. Some of these techniques, which depart from the traditional ones, are called "extended techniques". In this thesis, some of these techniques have been mentioned and even investigated. One is circular breathing, where the player inhales while maintaining airflow from a reserve volume stored in the mouth cavity. This technique was even used as an experimental task in Paper IIIb. Other extended vocal techniques, such as vocal-ventricular mode phonation, periodic pulse phonation (Strohbass) and growl, are all considered in Paper VI.
Vibrato is a conventional and widespread effect in music. It has been an object of study from different areas, such as music acoustics (Meyer, 1991; Prame, 1994, 1997), music perception and psychology (Seashore, 1932, 1936, 1937, 1938; Brown, 1991), electronic music, and physiology (Gärtner, 1973; Titze, 1994; Hirano et al., 1995).
More effort seems to have been invested into the understanding on how vibrato is generated, than into how it can be practised and taught. Yet, the mechanism generating the vibrato in the wind instruments considered here is far from being exhaustively elucidated. Many musicians and even educators support the idea that vibrato develops "naturally", provided the playing technique is appropriate, and the instrument is "tuned" and properly set. The physical and physiological interpretation of these conditions is however unclear. Against this background it seemed important to examine physiological and aerodynamical aspects of vibrato production. This was carried out in Paper II.
Figure 12. An attempt to a musical parody of the sensorial homunculus representing a player's
somesthetic cerebral cortex in terms of the areas employed during music performance. Adapted from Penfield & Rasmussen (1950).
Playing a wind instrument is often associated with a complex of body movements. It requires a multitude of sensations, particularly those related to hearing, touch in embouchure and fingers, posture, and respiration. In order to illustrate the compatibility of the human tactile potentialities with wind instrument playing, the diagram in Figure 12 is provided, adapted from the classical picture presented by Penfield & Rasmussen (1950). The homunculus figure shows how the extroceptive sensations, i.e. those referring to tactile stimuli, temperature and pain, are represented on the cerebral cortex. The position and extent of the areas of the parietal cortex corresponding to the different parts of the body are mapped. The figure reveals that the lips, tongue and fingers occupy wide areas on the brain surface, particularly as compared with the correlative skin areas. A comparable diagram could be drawn with respect to motor functions, based on the motor homunculus proposed by the same authors.
Apart from the extroceptive sense, proprioception is highly important, being responsible for sensing the excitations in muscles, tendons and joints. This reflects body movement, position and, particularly in wind playing, blowing pressures and aspects of embouchure. In the case of embouchure, extroception and proprioception seem intricately related, since the contraction of the mouth muscles is converted into action on the oscillating reed, which feeds back an intense stimulation of the tactile receptors in the lips. In the case of perception of blowing pressure, however, it can be assumed that the main component is proprioceptive due to the fact that respiratory mechanics involve a great number of muscles, tendons and joints. This is suggested to dominate over the tactile sensitivity of intra-abdominal and trunk parts, as illustrated by the reduced cortical representation in the homunculus, Figure 12. In order to assess the proprioception of blowing pressure in wind players, independently of the other stimuli that usually concur during musical performance, an experiment was devised using a psychophysical production method, Paper V.
Figure 13. A diagram showing the breathing-related aspects and factors involved in wind instrument playing, and those selected for investigation in this thesis (in bold letters)
Given the multitude of factors involved in wind instrument playing, it was necessary to select those, which were both relevant and feasible to study, see Figure 13.
Blowing pressures were investigated in Papers I and II, where the relationship with pitch, airflow and loudness were considered. From the results it could be assumed that the perception of blowing pressure is a highly relevant factor in wind instrument playing. This assumption was tested in Paper V. Also, there was no detailed information on how those pressures and flow were generated in terms of respiratory movements. This issue was examined in Paper IV. Considerable variations in pulmonary gas, particularly CO2 and O2, can be expected during playing. These variations seemed great enough to affect the instrument's acoustical properties with respect to pitch. The variations and their effects were studied experimentally in Papers IIIa and IIIb. Composer's instructions are normally encoded in a score, representing the typical input to a player. It contains instructions regarding rhythm, dynamical level, pitch, breath pauses and phrasing, all factors considerably affecting the player's breathing and blowing. In our experiments it seemed advisable to use normal-looking scores in describing tasks, since the form of instruction may be relevant to the player's behaviour. The acoustics of the room represents a factor generally considered of major importance to music performance and hence to the players' behaviour. For example, the scaling of dynamic levels (Paper II) and the duration of breathing pauses (Paper IV) can both be expected to vary with this factor. Embouchure is another factor of great significance in wind instrument playing, as explained above. For reasons of limitation, these two last mentioned factors were not studied in depth in this thesis.
It should be borne in mind that the ways of playing reed woodwinds are not exhaustively definable. The instruments are still in their evolution process, in terms of both bore/tonehole design and mechanics, stimulated by a continuous contribution of new research and applied technologies, while still keeping a long-term manufacturing tradition, see Figure 14. New design and materials for the reeds are under continuous development and so is contemporary music, with new requirements and potentialities. Also, the demands on the professional musician are not static. For instance the interaction of mechanical and electronic intruments and multi-instrumentalism, for which the artist must be able to perform on different instruments may be helped by a technology and technique that combines some of the control particularities of different instruments. This development may be furthered by a systematic research in music acoustics and music performance.
Figure 14. The final rehearsal. Making an instrument requires meticulous craftsmanship and performance tests. Subtle modifications in form and dimension affect the sounding and playing properties. Photo by Blei & Baumann (1987).
©1998 by Leonardo Fuks
7.Basic ideas and methods
The basic idea behind our investigation on wind instruments was that respiratory acts in playing derives their characteristics from three different realms, (1) the acoustical properties of the instrument, (2) the physiological characteristics of the player, and (3) the musical demands of the score. As illustrated in Figure 1, these three realms are closely intertwined. To elucidate the relations between them, more detailed descriptions of the associated phenomena are needed. Such descriptions must be based on experimental work, requiring the use of an ensemble of methods of measurement as well as the selection of appropriate tasks.
Our research has been done with the assumption that the knowledge gathered from a predominantly physical approach should preferably be complemented by measurements collected under conditions that appear realistic to the players. This can be expected to result in additional and relevant aspects of the instruments influenced by the human factors in the relationship player/instrument.
The subjects in all wind instrument studies were adult healthy players, representing the western classical tradition. All subjects were either professional or semi-professional with more than 10 years of continuous experience. This was motivated by the belief that successful and experienced players use their instruments in a way that involves several processes of optimisation. Such optimisation can be expected as a result from long-term learning and experience and should lead to automated behaviour. This does not imply that there is a unique solution to any given performance problem, posed by the music, the instrument or the player’s physiological abilities and constraints. On the contrary, players can be expected to tailor their solutions to conditions represented by their instrument, and to their personal preference and physiology. No more than two players were used for each instrument. This was considered sufficient for the questions raised in the thesis, its main aim being to describe and explain aspects of wind instrument playing of players who are sufficiently skilled to earn their livelihood from playing. On the basis of our results, variations of playing technique should be more meaningful to examine in the future.
The experimenter strived for establishing a professional relationship with the subjects. All subjects were paid for their services, as artists should always be compensated when their professional competence is used. Moreover the payment may have contributed to eliciting a professional attitude to the solution of the various experimental tasks which were sometimes repetitive and demanded a high degree of concentration. The experimental sessions lasted for a full hour, approximately. The subjects were minimally informed about the purpose of the experiments.
It was considered desirable to ask the subjects to perform musically common tasks, such as scales, arpeggios, and well-known music examples. This was expected to induce their typical instrument playing behaviour.
Because the use of typical playing conditions was a main concern, methods that the player could regard as invasive or disturbing were avoided as much as possible. For the studies involving blowing pressure measurements, Papers I-II-IV-V, a thin pressure sensor (Gaeltec CTO-2 strain gauge catheter, 2mm diameter) was inserted in the player’s mouth corner and fixed to the face with adhesive tape. According to the subjects, this only marginally affected their embouchure. The respiratory inductive plethysmography (RIP) technique, applied in Paper V, is in essence a non-invasive method, since it measures external surface variations to infer internal thoracic volume changes. For the sake of accuracy, a fixed and rather symmetrical body posture is required. On some rare occasions the subject failed to meet this demand which caused interruption of the recording. In all such cases the professional player then promptly and successfully accomplished the repeating of the task with a stable posture. The use of the pneumotachometer (or electrospirometer) in Papers II-IV-V, did not cause any difficulties, since the subjects inhaled through it after exhalatory tasks, the mouthpiece being available from the hands of the experimenter whenever necessary.
In the investigation of vocal-ventricular phonation, Paper VI, several methods were used. For measuring the glottal flow, a Rothenberg mask (Rothenberg, 1973) was attached to the subject’s face, covering the mouth and the nose. This did not appreciably disturb sound production. In obtaining the images from the glottis by high speed filming, a rigid telescope was inserted in the subject’s mouth and held by the medical expert in the pharynx, allowing view of the ventricular folds. This method is clearly invasive, but it could successfully be applied after some attempts. For the preliminary videolaryngo-stroboscopy technique, a thin fiberoptic catheter was inserted through the nose and placed above the larynx. This did not disturb sound production. In recording subglottal pressure, a thin catheter was inserted through the nose, placed in the esophagus below the level of the larynx. Local anesthesia was required to prevent irritation and disturbance of voice production.
In the present thesis, we have strived for selecting questions which are both acoustically and musically relevant. In designing experiments a basic idea was to take advantage of the artists’ skills and long-term experience, thus hopefully attaining information collected under musically realistic conditions. Moreover, it was considered important that the scientist understand the artist’s frequently intricate questions.
©1998 by Leonardo Fuks
8. Summaries and comments on individualpapers
Paper I. "Blowing pressures in bassoon, clarinet, oboe and saxophone"
Blowing pressure is a major input parameter in wind instruments. In previous investigations, some data had been published on this topic (Bouhuys, 1964, 1968; Navrátil M & Rejsek K, 1968; Pawlowski & Zoltowski, 1985, 1987; Bak & Doemler, 1987; Cossette, 1993). However, there was a shortage of systematic measurements describing details of the relationship between pitch, blowing pressure and dynamic level. Also, some previous studies reported results collected from huge numbers of players, including professionals and students, presumably obscuring systematic dependencies between the three parameters mentioned. The aim of many of these studies was mainly to provide typical and maximal pressure values for clinical applications. The basic hypothesis tested was that a systematic relation exists between blowing pressures and the acoustic properties of the instrument and of the tones produced.
We recorded blowing pressures in the mouth cavity of two professional players of each of four reed woodwinds (Bb clarinet, alto saxophone, oboe, bassoon). The players performed three different tasks: (1) a series of isolated tones at four dynamic levels, (2) the same series with a crescendo-diminuendo tones and (3) ascending-descending musical arpeggio played legato at different dynamic levels (pp, mp, mf, ff). The results showed that, within instruments, the players’ pressures exhibited similar dependencies of pitch and dynamic levels. Between instruments, clear differences were found with regard to the dependence on pitch. As can be seen in Figures 14-15, 20-21, 26-27 and 32-33, each instrument presented characteristic curves, differing only slightly between players.
Vibrato was not an object of study in this project, and the players were asked to avoid it, since it could be assumed to be associated with variations of the blowing pressure. Yet, some players occasionally produced a vibrato, as can be seen in Figure 6, p 44. In that particular case, the average blowing pressure was approximately 13 cmH2O, while the amplitude of the vibrato oscillations varied between 1.5 and 3.0 cmH2O peak-to-peak. This considerable modulation (about 10-25%) was still associated with a rather moderate vibrato effect. For a greater vibrato and at higher dynamical levels and pitches, even larger pressure modulations can be expected. This issue was investigated in Paper II.
The investigation focused on isolated, sustained tones, crescendo-diminuendo tones and arpeggi at fixed dynamical levels. We might assume that similar patterns would be found for other notes in the range studied and that blowing pressures for intermediate notes can be estimated by interpolation (see Paper I, Appendix, Table A). However, the fingering and the instrument’s responsiveness do not necessarily vary continuously between adjacent tones, and this may demand differing pressure values. Tone variations occurring in the playing of real music may require much more complex pressure changes, see Figure 1, Paper V.
The Paper suggested that the proprioceptive functions in the respiratory system, which are responsible for the perception of stimuli by the abdominal, thoracic and lung receptors, are highly relevant to wind instrument playing. This was the main topic of Paper V.
The roles of the authors in this Paper were as follows: LF: Experimental design, recording, analysis of data, authoring the draft for the manuscript; JS: Consultation, assistance in experiment and in editing the manuscript.
Paper II. "Aerodynamic input parameters and sounding properties in naturally blown reed woodwinds"
This study can be considered a complementation of Paper I, which focused blowing pressure. The present paper corroborated and expanded the data from Paper I and added information regarding the airflow resistance of the reed. Also measurements of airflow were carried out, allowing estimation of typical demands on air supply in the different instruments - oboe, alto saxophone, bassoon, and clarinet.
Commercially available clarinet and saxophone reeds are usually specified with respect to "hardness", using an arbitrary scale ranging from 1 (soft) to 5 (hard). The "hardness" of a reed is defined by means of bending tests, i.e. in a way similar to that of measuring stiffness of materials in engineering (Vandoren Products Catalog, 1983). However, the "hardness" of a reed may be associated with a number of other properties as demonstrated by Fuks (1995) for clarinet reeds. Reed "hardness" is highly relevant to bassoon and oboe playing, and is generally adjusted by the players when they manufacture the reeds. The acoustical and aerodynamical correlates of the "hardness" have not been experimentally demonstrated. According to the general opinion among players greater "hardness" is associated with the need for higher blowing pressures and embouchure forces as well as with a "darker" tone quality.
Input aerodynamic parameters in reed woodwinds were measured when professionals played different pitches at three dynamic levels. Two reeds were used, one rated as a hard and another as a soft reed. The contrasting reeds in our experiment showed clearly different characteristics in terms of airflow, blowing pressure and resistance.
The tasks consisted of playing long sustained tones with and without vibrato. Audio and blowing pressure signals were recorded. Lung volume variations were indirectly measured by a spirometric procedure, which also showed the average air consumption, i.e. the mean airflow. The tones were played in a laboratory room and also in a calibrated reverberant chamber allowing estimation of radiated sound power. Average values for flow resistance, aerodynamical power, and mechanical efficiency were computed. Airflow and input power varied considerably between instruments and between the two reed types, but generally increased with sound level. Airflow systematically increased with blowing pressure and dynamical level in all instruments. The harder reeds required higher airflow, blowing pressure and tended to produce tones of higher SPL.
According to previous investigations the pressure-flow characteristic should follow a bell-shaped curve under conditions of constant embouchure tightness, see Figure 9, and only the falling part of the curve can be used in playing. Yet, our pressure measurements indicated that an increase of blowing pressure was associated with an increase of dynamic level. Thus, an increase of pressure seemed to produce an increase of airflow. This apparent discrepancy suggests that the player must reduce the embouchure tightness during a crescendo. If the player keeps a constant embouchure while increasing blowing pressure, the tone gets softer until eventually the reed simply closes.
Vibrato can be generated in different ways, as mentioned above. The investigation focused on an intense, or clearly audible vibrato. For vibrato tones produced on oboe, bassoon and saxophone, wide pressure oscillations were observed, on average 10 cmH2O for the oboe and bassoon, and reaching values of 20 cmH2O in some cases. These great undulations cannot be produced merely by the laryngeal mechanism, as claimed in previous studies, but must require participation of expiratory forces.
Paper IIIa. "Prediction of pitch effects from measured CO2 content variations in wind instrument playing"
Paper IIIb. "Prediction and measurements of exhaled air effects in the pitch of wind instruments"
Paper IIIa, limited to the effect of CO2 on tuning, was complemented by Paper IIIb, considering also the O2 effects. The latter paper was compressed in size, to meet the demands for the proceedings of a conference. Therefore, a more elaborate account will be given here, also including some complementary examination of the results.
The studies reported in Papers IIIa and IIIb departed from a pilot study about respiratory conditions under different degrees of physical exercise and the effect of CO2 in the lungs on maximal breathhold time. A capnometer, a device for measuring carbon dioxide percentage in the air (Bhavani-Shankar et al., 1995), was used for measuring CO2 variations during performance on the oboe and the clarinet. This is a key gas in the respiratory control; the human body contains receptors that continuously monitor the amount of that gas, regulating the optimum level of gas changes and the rhythm of ventilation (Staub, 1991; Shea et al., 1996; Piiper & Scheid, 1982; Klocke, 1982; Flume et al., 1996; Fernando & Saunders, 1995; Banzet et al., 1996).
We observed wide variations in the CO2 contents of exhaled air, usually starting from 2.5-3% and reaching up to 8.5% in extreme cases, after more than 50 seconds of playing without taking a new breath. This value exceeded those published as extremes in medical textbooks (e.g., Schmidt & Thews, 1983) and even in studies of the effects of breathhold during diving (Lin, 1987).
The effect of these great changes in gas composition on the intonation in these instruments was analysed. As mentioned, fundamental frequency depends on the sound speed in the air column in these instruments. Nedeerven (1969) calculated the effective sound speed for a flute, taking into account the effect of temperature and also the composition of the gas and assuming a CO2 average of 2.5%.
In Paper IIIa, the variations in exhaled O2 were assumed to vary linearly with time between 21% and 15%, the generally accepted range (Schmidt & Thews, 1983).
The study further assumed warmed up instruments, so that the temperature effect would not be interfering with the effect of gas composition. Also, it was postulated that the player started after a deep breath, inducing low values of CO2 and high values of O2. Simultaneous measurements of CO2 and O2 were realized in Paper IIIb.
Predicted and observed decreases of fundamental frequency amounted to 27 cents and 16 cents, respectively. The discrepancy might be accounted for by factors not considered in this paper. Thus, air humidity was assumed at a fixed 100% value, i.e., saturated vapour. As a complement, we present a calculation of the impact of humidity changes.
The idealised situation with a warmed up instrument is assumed, but with humidity increasing from ambient values to vapour-saturated air during the first moments of playing. As mentioned in Paper IIIa, sound speed c is calculated by equation 1.1,
an alternative equation, resulting from Boyle's law, is
P0 is the ambient pressure
r 0 is the gas density
g , the specific-heat ratio, i.e. specific heat at constant temperature divided by specific heat at constant volume
R , a gas constant
T is the temperature in K
R0 is the universal gas constant , 8312 J/(kg.K)
M is the average molecular wheight of the dry composite gas.
This formula yields the same numerical results as those obtained by formulas 1.1 and 1.2 in Paper IIIb. In accounting for the effect of humidity, a thermodynamic formula valid for the narrow range of variations in temperature and in gas compositions (e.g. Pierce, 1981) is:
cwet sound speed in the humidified gas,
cdry sound speed in dry gas,
H fraction of H2O molecules in the air
From thermodynamical tables (ASME, 1967) it can be calculated that for saturated vapour at 40°C, the value for H is 0.07, approximately (Pierce, 1981). For a variation from 40% ambient humidity to 100% inside an instrument, i.e. reaching 60%, the isolated contribution of humidity should be approximately:
According to Equation 5 the increase in sound speed due to humidity should amount to 0.67%, or 12 cents in fundamental frequency for the sounds produced. This amount should oppose the expected maximum shift of -27 cents, due solely to the CO2 and O2 changes. The net shift of -15 cents seems realistic, as compared to approximately -16 cents observed in Paper IIIb and shown in Figure 3.
As pointed out in Paper IIIa, the impact of the effect of the gas mixture should also indirectly depend on the airflow. Paper II offered some experimental data regarding airflow through four reed instruments. The volume contained in an adult player’s upper airways, or the physiological dead space, amounts to approximately 150 ml. In cases of low airflow, it could take as much as 3 or 4 seconds for the intrapulmonary air to reach the reed. This would be the most critical phase for the gas effects on the intonation, as shown by Figures 2 and 3 in Paper IIIb. During that period, the quasi-ambient air would be fed to the instrument bore, and thereafter intrapulmonary air. In cases of high flow, the effect of the transient gas density will occur at the same time as other transitional processes, such as the onset of the tone, the adjustment of pitch and dynamic level, etc. Once the pulmonary air has filled the entire instrument a slowly changing effect on the fundamental frequency can be expected.
Papers IIIa and IIIb demonstrated that the discussed effect of gas changes may be a relevant factor in performance.
The outcomes of this study can be demonstrated by a simple experiment that may be useful in a music classroom. It requires a reed woodwind instrument, a manometer connected to the player’s mouth and an electronic tuner. After warming up, the subject will play a long steady tone at pp, keeping a fixed embouchure and blowing pressure as displayed by the manometer. Another observer will monitor the fundamental frequency as indicated by the tuner. The subject may blow a long tone interrupted by occasional brief pauses, without breathing. This is not expected to change the tuning. Then, the subject quickly exhales the remaining air in the lungs and resumes playing after a quick and deep breath. This time, an effect on tuning can be expected. This obviously is a simplified and less well-controlled version of the experiment described in Paper IIIb.
Paper IV. "Respiratory inductive plethysmography measurements on professional reed woodwind instrument players"
In Paper II, airflow in long sustained tones, played at different pitches and dynamic levels was measured. This, obviously, is a rather particular playing condition. To collect data from real performance a different method should be applied. As mentioned, the multiple factors in sound production in wind instruments make it a hard task to measure airflow directly, without severely affecting the system.
Respiratory Inductive Plethysmography (RIP) is a technique devised for clinical respiratory monitoring, introduced in the end of the 70's. It is still in frequent use as it is reliable, robust, non-invasive, intrinsically safe and represents a relatively low cost method (Chadha et al. 1982; Strömberg, 1996). The technique is based on the principle of self-inductance of a coil, which is connected to a high-frequency oscillator. Elastic bands are wrapped around the chest and abdomen of the subject; the bands are provided with an electric coil powered by the oscillating unit, see Figure 1 in Paper IV. The changes in the cross-sectional areas surrounded by the coils cause changes in the electromagnetic properties of the system. Thus, the individual variations of chest and abdominal volumes produce corresponding variations in the output signal of the RIP. The method is closely related to the two-degrees-of-freedom model for measurement of chest wall volume displacements (Konno and Mead, 1967; Loring and Bruce, 1986). According to this model, the variations in lung volumes are solely reflected in the variations of the two independent compartments, the rib cage and the abdomen, although a good accuracy can be attained only provided that there is no change in body position. The technique has been successfully applied to the analysis of respiratory movements in singers (Thomasson and Sundberg, 1997). In addition, studies have been carried out on the relation between respiration and phonation (Iwarsson et al., 1996). Regarding wind instrument playing, one single investigation (Cugell, 1986) has been published, particularly considering brass instruments and presenting mainly qualitative data.
Since high pressures had been observed in playing (Papers I-II) and some wide respiratory movements could be expected, as compared to previous applications of RIP, suitability and accuracy were main concerns. One attempt to assess the method was to apply the RIP band around a calibrated cardboard box, which permitted oblique angular distortions, i.e. changes of rhomboid cross-sectional area while keeping constant perimeter, see Figure 15. As shown, the output of the system was linear for a wider range than that equivalent to abdominal dimensions.
Additional calibration procedures were used to check the RIP accuracy in the pressure and lung volume ranges used in wind instrument playing. These experiments are described in Paper IV.
The method was then applied to eight professional players of the four reed instruments, who performed different musical and respiratory tasks. It yielded acceptable accuracy for the measurement of lung volumes, relative abdominal and rib-cage movements and also for the temporal and kinematic details of brief breathing pauses. Particularly challenging demands on respiratory technique were presented in terms of JS Bach's piece (solo obligatto from Cantata 147). Its long, "motoric" phrases played at a fast tempo, did not offer suitable breathing spots to the players. This reflected on the respiratory patterns and also as short duration of the breath pauses. The RIP method turned out to be appropriate even under these extreme conditions. It thus seems applicable to wind instrument performance research in general and should be useful also in pedagogy. In addition, a computer program was written and implemented for the use in portable computers with an acquisition card, allowing real-time calibration and data display.
Figure 15. Test of RIP linearity: squares show the linear output obtained when the angles of a rhomboid box, fixed perimeter of 108 cm, with a RIP band attached, were changed. The line represents the best linear fit (R2=.997). Filled circles show minimum and maximum output voltages for abdominal cross-sectional area in a subject.
Breath groups were initiated at 55% - 87% and terminated between 14% - 52% of the players’ vital capacity, depending on instrument, piece, and phrase length. The players generally showed simultaneous and in many cases equally important contributions from rib cage and abdominal wall during playing. These findings often contrasted sharply to the players’ own ideas on how they used their respiratory apparatus. The findings departed from what had previously been found for singers, who tend to resort mainly to chest wall movements for generating lung volume changes. In extreme cases, inhalations were achieved in approximately 300 ms and reasonably synchronised with the RIP signals.
The roles of the authors in this paper were as follows:
LF: Pilot studies on the RIP method, using different calibration procedures and carrying out recordings and data processing from the performance of several musical tasks with the different instruments; design of the experiment; running the experiments; processing of experimental data; writing of the paper; discussion of paper with co-author JS
JS: discussion on experimental protocol; running the experiments; writing of the paper; discussion of paper with co-author LF
Paper V. "Assessment of blowing pressure perception in reed wind instrument players"
Paper V was exploratory in nature since it represented, to our knowledge, the first study ever on this modality of perception in musicians. Paper I showed that professional players change blowing pressure systematically according to instrument, pitch and dynamic level. This indicates that players must possess the ability to accurately sense the pressures they generate. It is obviously a prime control variable along with other parameters, such as the auditory feedback and the sensations in the embouchure.
The investigation applied a psychophysical production method for direct assessment of the blowing pressure perception in professional players. The main object of the study was the investigation of how the players judged mouth pressure, independently of normal playing conditions, i.e. without embouchure effort, reed vibration, airflow or auditory feedback.
The players were asked to produce static mouth pressures corresponding to a set of numbers that were given to them, one by one and in random order. The pressures thus produced were recorded and measured and then compared with these numbers.
The method provided consistent data representing interesting information about this rarely studied modality. Regression analysis revealed that a linear model yielded the highest correlation between measured and perceived pressures. Linearity is not generally found for other perceptual modalities, such as loudness and pitch. The method, however, did not allow for the estimation of the difference threshold, a relevant parameter for quantifying sensation.
The considerable inter-individual differences in sensitivity indicate that average values are not adequate to predict the behaviour of subjects in general terms. We used a limited group of subjects, all of them players of reed woodwinds. It would be worthwhile to include more subjects and players of other wind instruments in future investigation. To complement the result of this paper, other methods could be applied in the future, such as cross-modality comparisons.
Paper VI. "A self-sustained vocal-ventricular phonation mode: acoustical, aerodynamic and glottographic evidences"
Human voice is a result of a complex interaction between anatomical, physiological, neurological and cultural factors. The immense variety of vocal sounds encountered across the cultures of the world demonstrates a multitude of possibilities for using the voice organ (e.g. Zemp, 1996).
The role played by the ventricular folds (Figure 1 in Paper VI) in voice production still constitutes an open issue. Some authors suggested that the ventricular folds were responsible for producing the lowest tones, while the vocal folds would be generating the higher tones. It even has been claimed that the ventricular folds produce falsetto tones, speculations that were refuted already by Garcia (1855). Yet, it has remained unclear how the ventricular folds can be used in sound production, e.g., under pathological conditions such as in ventricular dysphonia (Freud, 1962).
A particular vocal effect, found in certain Asian cultures (Tibet, Mongolia), is associated with a very low fundamental frequency and a dense spectrum. This type of voice production had been documented in previous studies in voice science, ethnomusicology and music acoustics (Smith et al., 1967; Campbell & Greated, 1987; Barnett, 1977; Ellington, 1970), however without exhaustive explanation of the underlying sound production mechanism.
The initial hypothesis was that the mechanism employed includes the ventricular folds. For some years the first author attempted to learn this particular phonatory technique assisted by analysis resources provided at KTH-TMH. The attempts were successful according to expert testimony. This appeared to justify the use of the first author as a subject in the experiment, particularly since Tibetan monks in Sweden seemed hard to access.
Co-operation with the Karolinska Institute, offered the possiblility to obtain images derived from two different techniques, videolaryngo-stroboscopy and high-speed glottography.
The results of Paper VI revealed that, under special conditions, the ventricular folds vibrate periodically in cooperation with the vocal folds. Results did not corroborate the initial hypothesis that the ventricular folds vibrate in a reed-like fashion, i.e., as an inward striking valve. Rather, they vibrated more like the vocal folds and seem to importantly contribute to the primary sound generation in the mode of phonation used in Tibetan chant. The results suggested that, in spite of striking similarities with regard to spectral appearance, this type of voice production is different from the one used in the production of periodical vocal fry, such as in the so-called Strohbass register.
The participation of the authors in the paper was as follows:
LF: idea, planning and design of experiments, serving as the sole subject, data analysis, design of the VVM model, writing of first draft
JS: revision and discussion of the manuscript
BH: providing the possibility to high-speed imaging, expert advice and revision of the manuscript
©1998 by Leonardo Fuks