Ninety-and-nine persons if asked the question, what produces tone in the human-voice, would reply, "the vibrations of the vocal cords,"

and stop there, as if that were all; whereas the answer is very incomplete--not even half an answer.

A great deal of the irrational and injurious "teaching" of singing that prevails everywhere, and of the controversy that befogs the subject, is due to the widely prevalent notion that the little vocal cords are the princ.i.p.al cause of tone, whereas they are in themselves insignificant as sound producers.

=It is the vibrations of the air in the resonance chambers of the human instrument, together with the induced vibrations of the instrument itself, which give tone its sonority, its reach, its color, and emotional power.=

That this is not an empirical statement but a scientific fact, a few simple experiments will demonstrate.

Tone, in the musical sense, is the result of rapid periodic vibration.

The pitch of tone depends upon the _number_ of vibrations in a given period; the loudness of tone depends upon the _amplitude_ of the vibrations; the quality of tone depends upon the _form_ of the vibrations; and the form of the vibrations depends upon the _resonator_.

The fact that pure white light is a compound of all the tints of the rainbow into which it may be resolved by the prism is well known, but the a.n.a.logous fact that a pure musical tone is a compound of tones of different rates of vibration, tones of different pitch, is not so much a matter of common knowledge, and not so obvious.

a.n.a.lysis shows that a musical tone consists of a fundamental note and a series of overtones.[5] The ear is quite capable of recognizing many of these overtones and may be trained to do so. The most obvious can be readily separated from a fundamental by a simple experiment.

[Footnote 5: For fuller exposition see Tyndall on _Sound_, or the section devoted to _Acoustics_ in any text-book on Physics.]

The overtones arrange themselves in a definite order, as follows: (1) the fundamental or prime tone; (2) an overtone one octave above the fundamental; (3) an overtone a fifth above No. 2; (4) an overtone a fourth above No. 3 (two octaves above the fundamental); (5) an overtone a major third above No. 4; (6) an overtone a minor third above No. 5. There are others in still higher range but those indicated are easily demonstrated on the piano. For C they would be as follows:

[Music ill.u.s.tration]

Experiment I

Step to your piano, noiselessly press and hold down the key of No. 2, then strike the fundamental No. 1, with force and immediately release it. As a result No. 2 will sound clearly, and if your ears are keen you will at the same time hear No. 6. In succession hold down the keys of 3, 4, 5, and 6, while you strike and release the fundamental No. 1.

If your piano is "in tune" you will probably hear No. 6 when holding the key of any other note of the series.

In a musical tone of rich quality the overtones just indicated are present in their fulness, while tone that is weak and thin is made so by the absence or weakness of the overtones. I have stated that the quality of a tone depends on the _form_ of its vibrations, and that the form of its vibrations is determined by the character of the _resonator_. We can now amplify this by saying that while the relative presence or absence of overtones determines the clang or color of a tone, their presence or absence is determined by the _character of the resonance_.

An English writer records that he was once in the garden at the back of a house while a gentleman was singing in the drawing-room. The tone-quality was good, and the pitch so unusually high he hastened to learn who sang tenor high C so beautifully. On entering the room, instead of the tenor he had supposed, he found the singer was a baritone, and the note sung was only middle C. The fundamental tone had not reached him in the garden but the first overtone, an octave above it, had. Concrete ill.u.s.trations will make the subject still clearer.

Experiment II

If an ordinary tuning-fork when vibrating is held in the hand its intrinsic tone is too weak to carry far. Rest the handle of the vibrating fork on a bare table or the panel of the door, and the sound is greatly augmented. _The vibrations of the fork have by contact induced similar vibrations in the wooden table or panel which reinforce the primary tone._

Experiment III

Place the handle of the vibrating tuning-fork on a small upturned empty box, or, better still, in contact with the body of a violin, and the sound will be stronger than in the previous experiment, because to the vibrations of the wood are added the vibrations of the air enclosed in the box or the violin. _To the resonance of the wood has been added the sympathetic resonance of the confined air._

Experiment IV

Hold the vibrating fork over the mouth of an empty fruit-jar and there will probably be little or no reinforcement; but gently pour in water, thereby shortening the air column within the jar, and the sound of the fork will be gradually intensified until at a certain point it becomes quite loud. If you pour in still more water the sound will gradually become feebler. This shows that _for every tone an air column of a certain size most powerfully reinforces that tone_.

Experiment V

As a sequence to the last experiment, take two fruit-jars of the same size, and, having learned to what point to fill them for the greatest resonance, fill one jar (after warming it) to the required point with hot water, the other with cold water, and you will find that the resonance of the heated, therefore expanded, air is much less than the denser air of the cold jar. This shows that _the degree of density of the air affects its resonance_.

Experiment VI

To demonstrate the resonance of the oral cavity, apart from the voice, hold a vibrating tuning-fork before the open mouth. Vary the shape and size of the cavity until the sound of the fork suddenly increases in volume, showing that the right adjustment for resonance has been made.

_This intensification of the sound is due to the vibration of the air in the mouth cavity, together with the sympathetic vibration of the surrounding walls._

Experiment VII

As an ill.u.s.tration of sympathetic resonance without contact, sing forcibly a tone that is within easy range, and at the same time silently hold down the corresponding key of the piano. On ceasing to sing you will hear the tone sounding in the piano. This may be further ill.u.s.trated by playing on the open string of one violin while another, tuned to the same pitch, rests untouched near by. Through _sympathetic resonance_ the corresponding string of the second violin will vibrate and sound its note. The louder the first violin is played the louder will be the sympathetic tone of the second.

The deep pedal-tones of a church organ often induce sympathetic resonance that may be felt beneath the feet of the listener. One writer, a singer, speaks of living in the same house with two deaf-mutes. He lodged on the first floor, they on the third. One day, meeting at luncheon, one of the deaf-mutes told the singer that he had begun practice earlier that morning than usual. Surprised, the writer asked how he knew. The deaf-mute replied that they always knew when he was singing because they felt the floor of their room vibrate.

If tone vibrations can be transmitted so readily throughout a house, it is not difficult to understand how easily the vibrations of bone and tissue can be transmitted until the whole framework of the body responds in perceptible vibration.

It is said that Pascal at the age of twelve wrote a dissertation on acoustics suggested by his childish discovery that when a metal dish was struck by a knife the resulting sound could be stopped by touching the vibrating dish with a finger.

With this in mind it is not difficult to understand how compression of the human instrument by the pressure of tight clothing without, or by false muscular tension within, must interfere with its free vibration and so rob the produced tone of just so much of perfection.

From these experiments we can understand that, while the tones of the voice are initiated by or at the vocal cords, the volume and character of the tones are dependent upon _resonance_,--the vibration of the air in the various resonance chambers of the body, together with the sympathetic vibration of the walls of these chambers and the bony framework that supports them.

In respect to resonance, as in other respects, the human voice is far superior to all other instruments, for their resonators are fixed and unchanging, while the human resonator is flexible,--in Helmholtz's words "admits of much variety of form, so that many more qualities of tone can be thus produced than on any instrument of artificial construction."

We are now prepared to realize the error of the common notion that loudness of tone is due entirely to increase of breath pressure on the vocal cords. Simple experiments with the tuning-fork have shown that while the volume of sound it gives forth is due in part to the amplitude of its vibrations, its loudness is _chiefly_ due to the character of the _resonance_ provided for it.

The larger the resonance chamber the greater is its reinforcing capacity. The largest air chamber in the body is the chest, which serves not only as a wind-chest, but as a resonance chamber. The necessity for chest expansion, therefore, is not, as generally supposed, merely for air, but to increase its size as a resonance chamber.

In view of the laws of tone, how great is the common error of speaking of the larynx as if it alone were the vocal organ, when the princ.i.p.al vibrations are _above_ the vocal cords in the chambers of _resonance_!

Since the musical value, the beauty of tone, as well as its volume, comes only from right use of the resonator, our princ.i.p.al business must be the acquiring control of the vibratory air current _above the larynx_. The acquirement of this control involves the proper focusing or placing of the tone, with the free uncramped use of all the vocal organs; power will then take care of itself.

CHAPTER VII

HEAD AND NASAL RESONANCE

Of the four component factors in the production of speech and song, the first, the _motor_, has been considered in Chapter III, and the second, the _vibrator_, in Chapter I.

In one respect there is marked contrast between these two factors.

Until right habits are so thoroughly formed that the singer's breathing is automatically controlled, conscious effort is necessary, while the action of the vibrator, the vocal cords, is involuntary, not subject to conscious control.

The subtle adjustments of the delicate mechanism of the larynx belong to the realm of reflex action--to a spontaneous activity that, left unhindered, does its part in perfect nicety.

The vocal cords must, in their action, be free from the disturbance of uncontrolled breath action below them, or the hindrance due to misdirected effort above them. To direct consciousness to the vocal cords is to cramp them and prevent that free vibration and that perfect relaxation of the throat without which pure tone and true pitch are impossible.