CHAPTER VI

SCIENTIFIC KNOWLEDGE OF THE VOICE

So far as any definite record can be made, the knowledge of the voice obtained by attentive listening to voices has now been set down. The next step in the scientific study of tone-production is the consideration of all knowledge of the voice obtained from sources other than empirical. In other words, the knowledge of the voice usually classed as scientific is now to be examined.

Three sciences are generally held to contribute all that can possibly be known about the vocal action. These are anatomy, acoustics, and mechanics. Of these anatomy has received by far the most attention from vocal scientists. The laws of acoustics, bearing on the voice, have also been carefully considered. Beyond the theory of breath-control, little attempt has been made to apply the principles of mechanics in Vocal Science. Psychology, the science most intimately concerned with the management of the voice, has received almost no attention in this connection.

A complete record of the teachings of the established sciences with regard to the voice demands the separate consideration of the four sciences mentioned. Each will therefore be treated in turn. In the case of each of these sciences it is seen that the most essential facts of the vocal action have been definitely established. Many questions still remain to be satisfactorily answered which are of great interest to the theoretical student of the voice. Yet in spite of the lack of exact knowledge on these points, enough is now known to furnish the basis for a practical science of Voice Culture.

_The Anatomy of the Vocal Mechanism_

This subject has been so exhaustively studied that nothing new can well be discovered regarding the muscular structure of the vocal organs. In all probability the reader is sufficiently acquainted with the anatomy of the larynx and its connections. Only a very brief outline of the subject is therefore demanded. The muscles concerned with breathing call for no special notice in this connection.

The special organ of voice is the larynx. This consists of four cartilages, with their connecting ligaments,--the thyroid, the cricoid, and the two arytenoids, and of nine so-called intrinsic muscles,--two crico-thyroid, right and left, two thyro-arytenoid, two posterior crico-arytenoid, two lateral crico-arytenoid, and one arytenoideus. The inner edges of the thyro-arytenoid muscles form the vocal cords. The hyoid bone, serving as a medium of attachment for the tongue, may also be considered a portion of the larynx. By means of the extrinsic muscles the larynx is connected with the bones of the chest, neck, and head.

While the muscular structure of the vocal organs is thoroughly known, the actions of the laryngeal muscles in tone-production have never been absolutely determined. This much is definitely established: Vocal tone is produced when the vocal cords are brought together and held on tension, and the air in the lungs is expired with sufficient force to set the vocal cords in motion. The tension of the vocal cords can be increased by the contraction of their muscular tissues, the two thyro-arytenoid muscles; further, increased tension of the cords can also result from the tilting of the thyroid cartilage on the cricoid, by the contraction of the crico-thyroid muscles.

It is also definitely proved that the pitch of the vocal tone varies with the state of tension of the vocal cords; increasing the degree of tension raises the pitch, decreasing the tension lowers it. As to the relative importance of the different groups of muscles in varying the tension of the vocal cords, nothing has been definitely proved.

In addition to the variations in pitch resulting from variations in the tension of the vocal cords, there is also much ground for believing that the pitch may be raised by shortening the effective length of the vocal cords. This is apparently accomplished by the rotation of the arytenoid cartilages; but the specific muscular contractions concerned in the rotation of the arytenoids have not been located.

It is generally asserted by vocal theorists that the quality of the vocal tone, on any one note, is determined mainly by the influence of the resonance cavities. Dr. Mills says on this point: "When it is borne in mind that the vocal bands have little or nothing to do with the quality of the tone, the importance of those parts of the vocal apparatus which determine quality... becomes apparent." (_Voice Production in Singing and Speaking_, 1906.) This theory that the quality of the tone is determined solely by the resonance cavities is directly contradicted by Prof. Scripture. He proves that changes in tone quality result from changes in vocal cord adjustment. This subject is more fully treated in the following section. Even before this matter had been definitely settled by Prof. Scripture, there was a strong presumption in favor of the vocal cord adjustment theory. Howard advanced this idea in 1883. Several empirical observations support this theory. Most important of these is the fact that a single tone, swelled from _piano_ to _forte_, goes through a wide variety of changes in quality. Stockhausen's mention of this fact has already been noted.

This fact tends to cast some doubt on the value of laryngoscopic observation as a means of determining the laryngeal action. Under the conditions necessary for examination with the laryngoscope it is impossible for the singer to produce any but soft tones in the head quality of voice. Most of these tones, if swelled to _forte_, would change from the head to the chest quality. It is probable that this change in quality is effected by a corresponding change in the vocal cord adjustment, as the conditions of the resonance cavities remain the same. But this cannot be determined by laryngoscopic observation.

So far as the actions of the laryngeal muscles are concerned, no difference can be defined between the correct vocal action and any improper mode of operation. Sir Morell Mackenzie examined a large number of people with the aid of the laryngoscope; of these, some were trained singers, others, while possessed of good natural voices, had had no vocal training whatever. Many variations were noted in the notes on which changes of register occurred. But it could not be determined by this mode of examination whether the subject was a trained singer or not.

If there is one specifically correct mode of operation for the vocal cords, this correct action has never been determined from the anatomy of the organs. No doubt there is some difference between the muscular actions of correct tone-production and those of any incorrect operation of the voice. But the nature of this difference in muscular action has never been discovered by means of dissections of the larynx, nor by laryngoscopic observation.

_The Acoustic Principles of Tone-Production_

An outline of the existing state of knowledge regarding the acoustic principles of tone-production must be drawn mainly from one source. This is the latest authoritative work on the subject, _The Study of Speech Curves_, by E. W. Scripture (Washington, 1906). In this work Prof. Scripture overthrows several of the conclusions of Helmholtz which had hitherto furnished the basis of all the accepted theories of vocal acoustics. Considering the eminently scientific character of all Prof. Scripture's research work, his thorough acquaintance with every detail of the subject, and the exhaustive attention devoted to this series of experiments, we are fully justified in accepting his present statements as conclusively proved.

A first impression received from a careful reading of _The Study of Speech Curves_ is that the subject is vastly more intricate than had formerly been believed. Helmholtz's theory of vocal acoustics was fairly simple: The vocal cords vibrate after the manner of membranous reeds; a tone thus produced consists of a fundamental and a series of overtones; vowel and tone quality are determined by the influence of the resonance cavities, which reinforce certain of the overtones with special prominence. This theory is discarded by Prof. Scripture. "The overtone theory of the vowels cannot be correct." In place of this simple theory, Prof. Scripture reaches conclusions too complicated to be given in detail here. A brief outline of the subject must suffice for the needs of the present work.

Prof. Scripture found that the nature of the walls of a resonating cavity is of more importance than either its size, shape, or opening. A flesh-lined cavity is capable of reinforcing tones covering a range of several notes. Further, the vowel sound, and presumably also the tone quality, are determined more by the action of the vocal cords than by the adjustment of the resonance cavities. "The glottal lips vibrate differently for the different vowels." This adjustment of the glottal lips "presumably occurs by nervously aroused contractions of the fibers of the muscles in the glottal lips." Continuing, Prof. Scripture says:

"Physiologically stated, the action for a vowel is as follows: Each glottal lip consists mainly of a mass of muscles supported at the ends and along the lateral side. It bears no resemblance to a membrane or a string. The two lips come together at their front ends, but diverge to the rear. The rear ends are attached to the arytenoid cartilages. When the ends are brought together by rotation of these arytenoid cartilages, the medial surfaces touch. At the same time they are stretched by the action of the crico-thyroid muscles, which pull apart the points of support at the ends.

"In this way the two masses of muscle close the air passage. To produce a vowel such a relation of air pressure and glottal tension is arranged that the air from the trachea bursts the muscles apart for a moment, after which they close again; the release of the puff of air reduces the pressure in the trachea and they remain closed until the pressure is again sufficient to burst them apart. With appropriate adjustments of the laryngeal muscles and air pressure this is kept up indefinitely, and a series of puffs from the larynx is produced. The glottal lips open partly by yielding sidewise,--that is, they are compressed,--and partly by being shoved upward and outward. The form of the puff, sharp or smooth, is determined by the way in which the glottal lips yield; the mode of yielding depends on the way in which the separate fibers of the muscles are contracted.

"These puffs act on the vocal cavity, that is, on a complicated system of cavities (trachea, larynx, pharynx, mouth, nose) with variable shapes, sizes, and openings. The effect of the puffs on each element of the vocal cavity is double: first, to arouse in it a vibration with a period depending on the cavity; second, to force on it a vibration of the same period as that of the set of puffs. The prevalence of one of the factors over the other depends on the form of the puff, the walls of the cavities, etc."

Prof. Scripture does not undertake to point out a difference between the correct vocal action in tone-production, and any incorrect action. This difference in action does not seem capable of definition by any analysis of the acoustic principles involved.

_Mechanical Principles of the Vocal Action_

In Part II, Chapter II, it was seen that the outflow of the breath in tone-production is checked by the vocal cords, in accordance with Pascal's law of fluid pressures. Another law of mechanics bearing on this operation is now to be considered, viz., the law of the transformation and conservation of energy.

The application of the law of the transformation and conservation of energy to the operations of the voice is nicely illustrated by the well-known candle-flame test of (supposedly) breath-control. To perform this test the singer is instructed to practise the exercises for breath-control while holding a lighted candle with the flame an inch or two in front of the lips. According to the idea of the breath-control advocates, the expired breath should escape so slowly, and with so little force, that no current of air can be detected at the lips, the expiration therefore does not cause the candle flame to flicker.

Describing the toneless breathing exercises to be practised with the candle flame, Browne and Behnke say, "Let it be observed that the above exercise is quite distinct from the well-known practice of _singing_ before a lighted candle, which is, comparatively speaking, an easy matter." (_Voice, Song, and Speech_.) A very striking fact is stated correctly by Browne and Behnke,--there is no current of air created at the lips during tone-production. Of the truth of this statement the reader may readily convince himself by trying this same experiment with a candle flame, or even with a lighted match. Hold a lighted match just in front of the lips and sing a powerful tone. The quality of the tone is of no consequence so long as it be powerful. Just sing, shout, yell, the louder the better. You will find that the flame is less affected under these circumstances than by the quiet expiration of ordinary breathing.

Considerable practice and close attention are required in order to hold back the breath in toneless breathing exercises. Whereas in producing any kind of powerful tone the breath normally creates no current of air at the lips.

There is no reason for considering this experiment a test of correct tone-production. It is impossible to produce a powerful tone of any kind, good, bad, or indifferent, and at the same time to create an appreciable current of air at the lips.

Needless to say, the breath-control theorists have entirely failed to grasp the significance of the candle-flame experiment. Yet we have here a demonstration of the mechanical law of tone-production.

Considered as a mechanical process, tone-production occurs when the energy exerted by the expiratory muscles, in their contraction, is converted into energy of motion of the vocal cords.[8] In other words, tone-production is an example of the transformation of energy. The law of the transformation and conservation of energy must therefore apply to this operation. This law is stated as follows: "Energy may be transformed from any of its forms to any other form. When energy is thus transformed the quantity of energy in the resulting form or forms is equal to the quantity of energy in the original form."

[Note 8: This exposition of the mechanical principle of tone-production is intended to be graphic, rather than strictly technical. For the sake of simplicity, that portion of the expiratory energy expended in friction against the throat walls, tongue, cheeks, etc., is disregarded, as well as that expended in propelling the air out of the mouth, in displacing the same quantity of external air, etc.]

The mechanical operation of tone-production comprises the following transformations of energy: First, the energy exerted in the contraction of the expiratory muscles is converted into energy of condensation or elasticity of the air in the lungs and trachea. Second, this energy of condensation of the air is converted into energy of motion of the vocal cords. In other words, the expiratory energy is transformed into energy of motion.

One objection, at first sight very serious, may be offered against this statement: the amount of strength exerted in the contractions of the breath muscles seems many times greater than is accounted for in the motion of the vocal cords. The movements of the vocal cords are so slight as to be observable only with the aid of a specially devised apparatus, the stroboscope. Can all the expiratory force expended in tone-production show such a small result? This apparent objection is found to be groundless in view of the application in this operation of Pascal's law. As this topic was fully treated in Chapter II of Part II, no further explanation is required here.

The erroneous idea of vocal mechanics involved in the doctrine of breath-control is now fully exposed. Tone can be produced only when the expired air exerts a pressure on the vocal cords. There is no necessity for any conscious or voluntary check on the expiration. The energy of the expiration is expended in setting the vocal cords in motion. No energy of condensation is left in the expired air the instant it has passed the vocal cords. Beyond that point there is no expiratory pressure.

In one sense it is true that the expiration is "controlled" in tone-production. But this control is strictly an automatic action. The vocal cords are adjusted, by the appropriate muscular contractions, to move in response to the air pressure exerted against them. This action involves, as a necessary consequence, the holding back by the vocal cords of the out-rushing air. So long as the vocal cords remain in the position for producing tone, they also control the expiration. In this sense breath-control is an inseparable feature of tone-production.

All that need be known of the mechanics of the voice is therefore perfectly plain. The vocal cords are set in motion by the pressure against them of the expired breath. This operation is in accordance with Pascal's law and the law of the conservation of energy.

But this analysis throws no light on the nature of the correct vocal action. It is impossible for the voice to produce a sound in any way other than that just described. In speaking or in singing, in laughing or in crying, in every sound produced by the action of the vocal cords, the mechanical principle is always the same. Nor is the bearing of this law limited to the human voice. Every singing bird, every animal whose vocal mechanism consists of lungs and larynx, illustrates the same mechanical principle of vocal action.

Only passing mention is required of the fallacy of the breath-band theory. The idea of any necessity of relieving the vocal cords of the expiratory pressure is purely fanciful. How any one with even a slight understanding of mechanics could imagine the checking of the breath by the inflation of the ventricles of Morgagni, is hard to conceive.

_The Psychology of Tone-Production_

This subject was treated, in some detail, in Chapter V of Part II. In that chapter however we were concerned more with a destructive criticism of the idea of mechanical tone-production than with the positive features of vocal psychology. At the risk of some repetition it is therefore advisable here to sum up the laws of psychology bearing on the vocal action.

Considered as a psychological process, tone-production in singing involves three distinct operations. First, the mental ear conceives a tone of definite pitch, quality, vowel sound, and power. Second, the vocal organs prepare to adjust themselves, by the appropriate muscular contractions, for the production of the tone mentally conceived. Third, the fiat of will is issued, causing the muscular contractions to be performed. These three operations are executed as one conscious, voluntary act. Let us inquire to what extent consciousness is concerned with each operation.

As conscious volitional impulses, the mental conception of the tone, and the fiat of will to produce the tone, are well enough understood. These two operations call for no extended consideration. We are at present concerned only with the psychological laws bearing on the muscular adjustments of the vocal organs.

Muscular contractions result from the transmission to the muscular fibers of motor nerve impulses. These nerve impulses originate in the motor nerve centers. They can never, under any circumstances, rise into consciousness. Contractions of the voluntary muscles occur either as reflex or as voluntary actions. In both cases the motor nerve impulses originate in the same nerve centers. In the case of reflex actions these lower muscular centers alone are involved; in voluntary actions the originating of the motor impulses is "controlled" by consciousness. In deciding that an action shall be performed, and in what way it is to be performed, consciousness directs that each motor center involved shall send out the appropriate discharges of nerve impulse.

Complex muscular activities require the sending out of nerve impulses from various motor centers. Such activities are usually not performed instantaneously, but require a longer or shorter time. Thus we may consider it as one action for the writer to rise from his chair, to lower the window and adjust the shade, and then to return to his seat. In this case a large number of motor centers are successively involved; at the proper instant each center discharges its impulse. To this end the motor centers must be instructed when to come into activity.

This distribution of nerve impulse is effected by the power of coördination. In voluntary actions coördination is accompanied by conscious control.[9] But coördination is not a function of the higher cerebral centers, that is, of consciousness. How the connection is made between the higher cerebral centers and the lower motor centers is a complete mystery. All that can be said is that the ideas of movements are transmitted to the motor centers, and that these send out the appropriate motor impulses.

[Note 9: In this connection it is advisable to point out a difference between the meanings attached to the word "control" in psychology and in Vocal Science. The psychologist classes habitual movements as either automatic or controlled. Automatic movements are purely reflex; the individual does not consciously decide whether they shall be performed or not. Psychologically considered, the _control_ of a movement is simply the conscious volitional decision whether the movement shall be performed. To adopt the language of Psychology, we should speak of _voice management_, and of _breath regulation_, instead of vocal control, breath control, etc. In the following chapters the accepted psychological usage of the word "control" will so far as possible be adopted.]

Turning now to the muscular adjustments of the vocal organs, these adjustments are seen to be independent of conscious guidance. When a tone is mentally conceived the vocal organs adjust themselves, in response to some mysterious guidance, for the production of the tone. The vocal cords assume the appropriate degree of tension according to the pitch of the tone to be sung. Both the quality of the tone and the vowel are determined by the combined adjustments of the laryngeal muscles and of the muscles which fix the shape and size of the resonance cavities. The power of the tone is regulated by the force of the breath blast; for each degree of power some special adjustment of the vocal cords is required.

All these adjustments are executed as one concrete and individual act in response to the volitional impulse contained in the mental conception of the tone. The tone is conceived as a concrete whole. It is not normally broken up mentally into its four aspects of pitch, quality, vowel, and power. True, each one of these four characteristics of the tone may be separately considered by the singer. So also, to a certain extent, may the adjustments of the vocal organs be performed with special reference to one or the other characteristic of the tone. But in every case the muscular contractions are performed without direct conscious guidance. Whatever be the character of the tone mentally demanded, the vocal organs instantly adjust themselves to produce the tone.

What is meant by saying that the muscular contractions are performed without conscious guidance? Does this mean that the singer is unconscious of the muscular contractions? Not at all. Muscular sense informs the singer, more or less distinctly, of the state of contraction or relaxation of the various muscles of the vocal organs. The singer always knows fairly well the condition of the various parts of the vocal mechanism. What is meant is this: The singer does not consciously direct the vocal organs to assume certain positions and conditions, and does not instruct the various muscles to contract in certain ways. The singer does not need to know, and in fact cannot know, what muscular contractions are required to produce any desired tone.

Some connection exists between the organs of hearing and the vocal mechanism. That this connection has a physical basis in the nervous structure is fairly well established. "The centers for sight and for arm movements, for instance, or those of hearing and of vocal movements, have connecting pathways between them." (_Feeling and Will_, Jas. M. Baldwin, 1894.) The psychological law of tone-production is that the vocal organs adjust themselves, without conscious guidance, to produce the tones mentally conceived. In actual singing the practical application of this law is that the voice is guided by the ear.

This guidance of the voice by the ear is incessant. It must not be understood that the mental ear simply conceives a single tone, and that the vocal machinery then operates without further guidance. All the characteristics of the vocal tones,--pitch, quality, and power,--are constantly changing. These changes require corresponding changes in the muscular adjustments. The muscular contractions in turn are guided by the demands of the mental ear. As a psychological process, singing may therefore be analyzed as follows: The singer mentally sings the composition. In response to the ever varying demands of the ear the vocal organs adjust themselves to produce actually the sounds thus mentally conceived. The singer listens to these sounds and at every instant compares them to the mental conception. If the tones actually produced fail to correspond exactly to those mentally conceived, the singer instantly notes this variation and bids the vocal organs to correct it. The ear has therefore a dual function in singing. First, the mental ear directs the voice in its operations. Second, the physical ear acts as a check or corrective on the voice.

To sum up the psychology of tone-production, the singer guides or manages the voice by attentively listening to the tones of the voice. This is the only possible means of vocal guidance. The voice and the ear together form one complete organ.

But we are still apparently as far as ever from the specific meaning of the correct vocal action. That the voice instinctively obeys the commands of the ear may be true theoretically. In actual practice we know that this does not by any means always occur. Singers are often unable to get the desired results from their voices, even when they believe themselves to rely on the sense of hearing. There must therefore be some influence which under certain conditions interferes with the operations of the vocal organs. The problem of tone-production is thus seen to be one of psychology. It narrows down to this: What can interfere with the normal action of the voice and prevent the vocal organs from instinctively responding to the demands of the ear? A satisfactory answer to this problem will be found only by a consideration of all available knowledge of the voice, both empirical and scientific. This forms the material of the final division of the present work.