THE VOICE AND SPEECH. 639 
THE VOICE AND SPEECH. 
It is convenient to speak of the singing voice and the speak- 
ing voice, though there is no fundamental difference in their 
production. 
Since musical tones can be produced by instruments greatly 
resembling those of the human voice, it becomes evident that 
in explaining the human voice we must take large account of 
the principles of physics. 
It is to be remembered that sound is to us an affection of the 
nervous centers through the ear, as the result of aérial vibra- 
tions. 
We are now to explain how such vibrations are caused by 
the vocal mechanisms of animals and especially of man. 
The tones of a piano or violin are demonstrably due to the 
vibrations of their strings; of a clarionet to the vibration of its 
reed. But, however musival tones may be produced, we dis- 
tinguish in them differences in pitch, quantity, and quality. 
The pitch is dependent solely upon the number of vibrations 
within a given time as one second; the quantity or loudness 
upon the amplitude of the vibrations, and the quality upon the 
form of the vibrations. The first two scarcely require any fur- 
ther notice; but it is rather important for our purpose to under- 
stand clearly the nature of quality or timbre, which is a more 
complex matter. 
If a note be sounded near an open piano, it may be observed 
that not only the string capable of giving out the correspond- 
ing note passes into feeble vibration, but that several others 
also respond. These latter produce the over-tones or partials 
which enter into notes and determine the quality by which one 
instrument or one voice differs from another. In other words, 
every tone is in reality compound, being composed of a funda- 
mental tone and overtones. These vary in number and in rela- 
tive strength with each form of instrument and each voice; 
and it is now customary to explain the differences in quality of 
voices solely in this way; and this is, no doubt, correct in the 
main; but when two individuals, using successively the same 
violin, play a scale nearly equal in loudness and as much alike 
in all respects as possible, are we to explain our ability to dis- 
criminate when the one or the other may be playing (out of 
our sight) solely by the overtones? To answer this would lead 
us into very complex considerations, and we only raise the 
