Physiology Of The Vocal Organs
Only those cartilages, bones and muscles which directly or indirectly form a part of the vocal organ shall be described. Usually the three cartilages which form the principal part of the larynx, together with the vocal chords which they enclose, is referred to as the vocal organ. This is a common, but mistaken conception. One might as well refer to four walls as a house, leaving out of consideration the foundation on which the house was built, and the roof which covers it.
The larynx, it is true, is the most important part of the vocal organ. But if there were no muscles to set it in motion or bones to give these muscles a basis from which to contract, the singer’s chance would be very poor, indeed. Not much beyond a coughing sound could be emitted and certainly no musical sound could be produced.
The muscles which surround the larynx bear to it the same relation as the tongue and wheels bear to the wagon. Neither is complete without the other. Furthermore, the singer and speaker can learn to control the muscles (at least the tongue muscles, and they are the principal ones concerned in the voluntary production of artistic sound), but if he/she should even attempt to control the larynx, good tones would be impossible. Of course, the primary part from which sound is emitted are the vocal chords. These are enclosed within the larynx, and the larynx is the uppermost part of the trachea, or air tube, through which we breathe.
See Fig. 41 (From Lesson V); it is a very exact illustration of the lungs, the air tube and the larynx.
All these parts together are known as the respiratory apparatus. The air tube or trachea is, as its name implies, a hollow tube, consisting of from sixteen to twenty cartilages, each shaped like a ring, with the rear part flat. Between the flat part of the rings and the spine is placed the esophagus, or food pipe, which leads to the stomach. The air tube divides at its lower end into two principal parts and from these there are many small branches, all of them embedded in the lungs, as the roots of a tree are embedded in the earth. When the lungs expand, a partial vacuum is created, which is at once filled by the air rushing through the mouth and nose into the air tubes.
The upper end of the air tube is formed of three larger cartilages, which constitute the larynx or vocal tube. See Fig. 61:
The basis of the larynx is the cricoid or ring cartilage. Upon this rests the thyroid or shield cartilage. Upon this rests the thyroid or shield cartilage. Upon this rest the thyroid or shield cartilage. The thyroid cartilage is formed of two plates which unite in front. Their rear end stand apart, from which two horns extend, each into the hyoid bone above, and downward over the sides of the cricoid cartilage. Only the rear under part of the thyroid cartilage nearest the spine rests upon the cricoid, leaving an open space between them in front. The bone above the thyroid cartilage is of very great importance to the singer and speaker, because all tone-power and the ability to stretch the vocal chords depends upon the proper action of this tongue or hyoid bone. The hyoid bone is shaped somewhat like a horseshoe. It has a thick body in front. Out of this frontal body grow two long horns which extend backward and somewhat upward toward the spine and tongue. There are also two smaller horns in front. The two described cartilages and the hyoid bone are connected with each other by striped voluntary muscular bands of fibers, which draw them toward each other, combining the three parts into one solid tube, about as the three parts of a flute can be joined together to form one tube.
When, through this joining of the cartilages and hyoid bone, the fibers and muscles on the inner sides of this tube are brought toward each other and stretched, then these stretched-and-touching-each-other muscles are set into vibration by the breath coming from the lungs through the air tube. Thus tones are produced, changing the upper part of the air tube into the vocal tube.
A more detailed description of these important parts of the larynx is necessary to the practical understanding of the mechanism of the voice and to the appreciation of the fact that it is not possible to change or add to the bones which form the basis of the larynx, but that it is possible to develop to the utmost the muscles which connect with these bones, thereby making artistic singing and speaking not only possible, but an assured fact to all who are willing to study and practice.
The larynx lies in the center of the throat. It is a short tube of movable cartilages, within which lie the vocal chords. The changing of position and the stretching of these chords are accomplished by special larynx muscles.
The Cricoid Cartilage
The basis of the larynx is the cricoid or ring cartilage. It is a solid ring on the upper end of the air tube. It has the form of a ring somewhat narrow in the front and rises towards the rear into and between the plates of the thyroid cartilage. On both sides of the ring are two depressions, into which are fitted the arytaenoides (tooth cartilage).
In Fig. 30, both the cricoid and the arytaenoides cartilage and their relation to one another may be plainly seen.
The Thyroid Cartilage.
This cartilage consists of two four-cornered plates which join in the form of a large triangle, like an open book. The upper part of this triangle varies its projection in different people and is known as “Adam’s apple” (Fig. 62 below). The rear sides of the two plates continue upward and downward in the form of horns. The upper and longest horns serve to connect directly with the hyoid bone (tongue bone) above them. The shorter, lower horns, embrace the cricoid cartilage below. From this position the thyroid cartilage moves forward and downward, or backward, as if on pivots, and thus assists in stretching the vocal chords;
hence it is sometimes call the stretching cartilage.
The arytaenoids (Fig 63, No 2) are in general three-sides, irregular pyramids which stand on both sides of the back and uppermost parts of the cricoid cartilage.
As these little cartilages are enveloped in muscles, they fill out the rear or open space of the thyroid cartilage. The under inner side is hollowed out to fit upon the steep, sloping sides of the cricoid cartilage. From these points the cartilages are moved toward and away from each other by muscles which connect them with the cricoid and thyroid cartilages. Out of these arytaenoides grow the vocal chords (Fig 63 No 6), extending forward to the inner corner of the front of the thyroid cartilage. These vocal chords are muscles and fibers filling the space between the inner walls of the thyroid plates. Now whatever affects the movements of the little arytaenoid cartilages, at the same time also affects the vocal chords.
(See, also, Fig. 64, rear view of the larynx.)
The Hyoid Bone
This bone has the shape of a horseshoe. It lies directly above the thyroid cartilage and is attached to the rear part of the tongue between the third and fourth vertebrae of the spine. It is easily found by pressing against the corner made by the lower jaw and the throat. The middle and forward-stretching part of the hyoid bone is the hyoid body, rather thick and strong. Out of it extend two long horns which reach far back into the throat; also two shorter horns in front. From these horns, and from the body itself, extend muscles which, like ropes from a masthead, attach themselves to many different points of the head, jaw, neck and chest.
(See illustrations 61 and 62.)
This is a cartilaginous, fibrous body, growing out of the larynx, somewhat tongue-shaped and very elastic. Its purpose is to cover the vocal tube during the act of swallowing, and so prevent food from passing into the air tube. It has no vocal office whatever, though formerly thought to have some vocal effect.
But this has been entirely disproved. (See Figs. 61 and 64 – Epiglottis.)
On top of the arytaenoid cartilages are the so-called cartilages of Santorini. Beside these are the cartilages of Wrisberg. However, no detailed account need be given of them, as their influence is automatic.
Muscular Tendons Of The Larynx
The two principal cartilages of the larynx, the thyroid and cricoid, are connected with one another by strong muscular bands or tendons. The two downward extending short horns of the thyroid cartilage are fastened to the rear part of the cricoid cartilage; the front and sides of both these cartilages are likewise connected and joined by muscular fibers.
The object of the tendons is to hold the thyroid cartilage (its horn parts) firmly down upon the part where it joins the cricoid cartilage. The object of these connecting muscles is to allow movements between the thyroid and cricoid cartilages. The thyroid cartilage may thus be moved downward to the cricoid cartilage, stretching and tensing the vocal chords, and again relaxing them as it resumes its normal position.
The two arytaenoid cartilages, situated inside the thyroid or Adam’s apple, and upon the rear sides of the cricoid cartilage, are fastened by tendons which hold them firmly to their points of attachment to the cricoid cartilage,
as may be easily seen by a reference to Fig. 65.
This illustration also gives a very clear picture of the vocal chords which rise from the front corner of the Adam’s apple or thyroid cartilage. Stretching horizontally backward, each is fastened to one of the two arytaenoid cartilages. It is interesting to find that some modern anatomists call the vocal chords merely ligaments connecting the thyroid cartilage with the two arytaenoid cartilages, which, incidentally, also produce voice and are hence called vocal chords.
In the illustration you can see the vocal chords apart; the space between them is called the glottis; as long as they remain thus apart, no sound can be made. But when the two cartilages to which they are fastened are wheeled, turned, or rotated toward each other, which is done by special muscles, then the glottis is closed and sound is made possible. But to make musical sound the vocal chords must also be stretched and held tense. To stretch them, it is necessary that the thyroid cartilage be tilted downward in front, thus dragging or drawing the front points of the vocal chords downward also.
As the ligaments which hold the arytaenoides in place upon the cricoid cartilage, not only hold them firmly, but even pull backward, there is thus established a forward and downward pull in front and a backward pull in the rear, effectually stretching and tensing the vocal chords.
The larynx is connected below with the air tube by a strong muscular band running from the cricoid cartilage to the upper ring of the air tube. Above, it is connected with the hyoid bone by several bands which encircle the upper end of the thyroid cartilage and the hyoid bone above it.
Muscles Of The Larynx
You have already learned that there are muscles which move the entire larynx, either downward or upward; there are also muscles which move the separate parts of the larynx toward each other, and these latter must now be considered. These real muscles of the larynx move the thyroid and cricoid toward each other, and again they move the arytaenoides upon the cricoid, thus bringing together and stretching the vocal chords. The muscles which fill the space between the cricoid, thyroid and the arytaenoid cartilages are in practical reality the vocal chords. Nearly all these muscles are or can be made to vibrate and to produce musical sound.
The main reason, perhaps the only reason, why we have in the past had so little success in training the voice, was because in former centuries anatomy was unknown. But even in more recent time, when vocal anatomy was being studied more minutely, mistakes were made and transferred from one investigator to another.
If we examine the vocal chords from above, by means of a little mirror (laryngoscope) held against the roof of the mouth, while sound is being made, the vocal chords may be seen plainly, as two little bands of whitish muscles, which approach and separate according as sound is made or not. These two whitish bands were formerly assumed to be all of the vocal chords. This is the first great mistake made by the physiologists. Out of this mistake grew the second great mistake, namely: that the vocal chords were stretched only by the internal laryngeal muscles, those from cricoid, thyroid and the arytaenoid cartilages. The eternal muscles were entirely disregarded.
If you were to take a bird’s-eye view of a house with sloping roofs, you would see only the upper two lines of the roof and you could assume that this roof was the whole house. But looking upwards from the ground, you see a house to have cellar, walls and several stories, the roof being merely its uppermost covering. Therefore, what we see when we look at the vocal chords from above, is merely the roof, the upper end of the vocal chords, but not the main parts, for they cannot be seen from that point. These main parts of the vocal chords or vocal muscles, lie like shelves against a wall. The longest part of these three-cornered shelves is the part that rests against the side wall of the thyroid cartilage, reaching down even to the sides of the cricoid cartilage below.
We have, in fact, a long vertical line of muscles which increase in number and size from below upward, bulging strongly outward at the upper end, and there forming an oblique line. Now the horizontal line forming the upper ends of these vertical and oblique lines is what we can see from above, and no more. The top of a shelf is really the smallest part of it; the parts below constitute by far the largest share of its size.
The part of the vocal chords which may be seen from above is only the horizontal line of the shelf of muscles under it. Of course, if that horizontal line were all of the vocal chords, they would be comparatively easy to stretch, because that part is small, but when you continue the line downward, you find that there is much more material to the things which we call vocal chords. If we can succeed in using all or most of these muscles, the tone will be stronger, clearer and sweeter.
Also, the strength or loudness of a tone depends upon the size of the vibrating material. Just as a thick wire will give a louder tone than a thin wire, or a large bell a stronger sound than a small one, so the thicker the vocal chords, the stronger the tone. Going still further, the law of physics teaches us that the quality of a tone is directly dependent upon the loudness or strength of the tone, because a loud tone contains many overtones, while a weak tone contains but few.
The quality of a tone, its charm and sweetness, is the result of the overtones within the tone. Therefore, the secret of a superior voice is really this: We should be able to use the entire volume of vocal muscles, in which case we have both strength and quality. As long as our voices are weak, it is a sign that we are not using all of our vocal chords, but only a part of them. Not only that, but because we are using only a portion of our voice material, that particular portion is being strained; hence it is subject to hoarseness, irritations, coughs, etc.
You can now easily see that when physiologists made the mistake of assuming that the vocal chords consist of two small muscles only, they would naturally make a second mistake, that of assuming that little strength was needed to stretch these small muscles and that this minor stretching was accomplished by the internal muscles of the larynx.
These two mistakes have resulted in false teaching for hundreds of years. The voice teachers, of course, believe what the physiologists claimed. Added to which is the fact that musicians do not always think logically, but, as they deal in emotions, are guided more by their emotions than by hard facts.
If physiologists had realized the importance to the vocalist of utilizing ALL of the vocal chords with which Nature has provided him, in order to obtain a strong and beautiful voice, they would certainly have gone deeper and more carefully into the subject, and must have found that not ONE pair of muscles, but FIVE, constitute the sounding part of the human throat.
Surely they would then have realized that the stretching power of the internal muscles of the larynx is far too meager to stretch and hold tense these five pairs of vocal muscles; then they would have found that Nature has provided a simple, indirect means of stretching the vocal muscles, viz,; the powerful and easily controlled external muscles of the larynx.
The Vocal Chords
The vocal chords extend from the roots of the arytaenoids along the inner side of the two plates of the thyroid cartilage to the angle where these plates meet and form the sharp corner in front of the throat which we call the Adam’s apple. Since these edges of the vocal chords meet at the angle of the thyroid cartilage, they touch each other at that point, but are farther and farther apart, as they stretch across to the arytaenoides on the right and left sides of the cricoid upon which these rest.
The vocal chords are not thin muscles, as is sometimes supposed, resembling strings or wires; far from it. They are more like muscular bands, being in fact rather broad, as they extend from about the middle of the thyroid cartilage. Bearing this broad band shape of the vocal chords in mind, it can easily be seen that these bands do not touch each other throughout their entire width during phonation; if they did, no breath could get through to set them into vibration, and, of course, no tone would be possible. The vocal chords must approach each other in the form of a sharp edge. This is brought about mainly through other muscles which lie behind the real vocal chords and which help, by rotating the arytaenoides upon their pivots, to bring the edges of the vocal chords toward each other.
As these muscles contract, they force the outer parts of the vocal bands toward each other, bulging them in such a way that sharp edges appear which can easily be set in motion by the breath. But in performing this office they also perform another, in that they enlarge the vocal chords, making them much thicker.
In later lesson, on the laws of physics and of sound, we shall learn that a tone is either weak or strong in proportion to the amount of vibrating, tone-producing material. A thin chord will give much weaker tones than a chord four or eight times thicker. Now, if only the vocal chords vibrate, the sound can be only of a certain strength, no matter how much breath pressure may be brought to bear. The breath cannot change the vibrating material in the least, but since the muscles which lie between the vocal chords and the wall of the thyroid cartilage contract very sharply and force the vocal chords toward each other, and also into a sharp edge, they add their own size, density and strength to the vocal chords, and consequently they also vibrate with them, being, in fact, like one compact bunch of muscles, instead of several separate pairs.
We may compare this with the bass strings of a piano, where the wires are reinforced with additional wires which are tightly wound around them, thus making the original wires perhaps four to eight times heavier, and, of course, the tone much stronger and larger.
Anticipating later chapters, it must be said that, like the heavily covered piano wired, the reinforced vocal chords, being heavier, vibrate much slower, consequently a high tone is only possible when great stretching power exists, enabling the singer to stretch these reinforced vocal muscles sufficiently to obtain the number of vibrations needed for the higher tones. Any singer who develops this necessary stretching power is thereby raised from the ranks of mediocrity to a high artistic level. Those who have not this power can develop it until it is equal or even superior to that of the greatest singers the world now has or ever has had. This is no hypothesis, but a mathematical certainty.
In Fig. 63 the action of the vocal chords and the muscles behind them is plainly visible. The muscle in front (the thin white line) is the real vocal chord; those behind contract sharply, of course becoming shorter and thicker, and cause the chords on either side to bulge toward each other in a sharp edge; at the same time the arytaenoids are revolved so that the chords nearly or quite touch each other.
Fig. 66 shows still more plainly that the vocal chords can be reinforced and enlarged to an almost unlimited extent by the surrounding muscles (3,4,5), thereby adding more and more volume to the tone, and, of course, more audible overtones, thereby giving greater volume and greater beauty to the tone quality.
In Fig. 66 the vocal chords (2) are plainly visible as the first layer of muscles growing out of the points of the two arytaenoids (6) and meeting in the center of the thyroid cartilage (1).
Picture them as bands extending downward nearly to the cricoid cartilage. The empty space between them is called the glottis (8). Behind the vocal chords are other layers of muscles (3,4,5), which also run from the arytaenoides to the front of the thyroid cartilage.
Remembering that the arytaenoids rotate upon the top of the cricoid cartilage, it is evident that such a rotating action will bring the vocal chords, and with them, of course, all the muscles behind them, toward each other. This is exactly what happens in singing, and also, but to a less extent, in speaking. The nerves which supply these muscles stimulate them to contract and hold them during the musical phrase or spoken sentence, after which, as there must be a slight pause between sentences, or phrases, the muscles relax and resume their original shape, to be brought to instant contraction on the beginning of a new sentence.
It is of the utmost importance to keep in mind that the front attachment of the vocal layers of muscles grows out of the thyroid cartilage and is permanently fixed at that point. The opposite ends are moveable, because they are attached to the freely moving, rotating pair of arytaenoid cartilages. As the chords contracts, these arytaenoides wheel around. But if there were no other muscles, the artaenoides would be drawn forward, away from the back of the cricoid toward the front of the thyroid. To prevent this, muscles have been provided which hold these arytaenoids in place; in fact, they pull strongly backward, just as strongly as the chords pull forward, and thereby help in stretching the chords.
These backward-pulling muscles (7) arise out of the back of the cricoid and are fastened to the rear of the arytaenoides, where they are assisted by still other muscles in this backward pulling. The student is earnestly requested to examine these points closely, as they are of importance to him/her and to their understanding of the following lessons.
The day has passed when merely the thoughtless singing of exercises suffices to make an artist. Clear thinking and scientific reasoning alone are the keys which will open the door to vocal success. We are dealing with a substantial science, one that is as much a matter of fact as the playing of a piano or a violin. But the singer must be his own creator, so to speak; he cannot BUY a perfect voice, he must know WHAT to do and then DO it.
In another lesson it was said that Nature provided two means of stretching the vocal muscles; one, the internal, has just been described, the other, or external, which has also been given. Where, in opera, stage, concert or church, a full, rich, scintillating tone is required, a think, small voice has no chance against a modern orchestra or even an organ. The demands made by modern composers require a tone that from the slightest piano can be increased to a voluminous fortissimo. The pleadings of the softest whisper of longing must, if need be, increase to the utmost cry of intense passionate love or hate.
Nature has made full and overflowing provision for all this. The vocal muscles, as they lie within the confines of the larynx, can stretch but little. The space from the thyroid to the arytaenoides is too small. It is only when the thyroid cartilage is tilted downward that the stretching can be increased. This action must take place before the chords can be completely stretched. And this stretching is accomplished by the external muscles already described. The external stretching of the vocal chords is voluntary and under the student’s control. The method can be learned by anyone who will give the subject a little intelligent consideration and sufficient practice.