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 principal 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 principal 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.