n of the same pitch that come from a harp, a violin, a
trumpet, a flute or from the human voice. Between two violins of exactly
the same make, played on by the same person, there would be greater
difficulty in discovering differences in the quality of tone, although,
even if made after the same pattern and about the same date, there
probably would be minute structural differences that would differentiate
their timbre to a musical ear; while if, of two violins, one of the
instruments were new, and the other old, a musical ear probably would
immediately detect differences in their tone-quality.

It is easier to distinguish between voices even of the same range,
than between instruments of the same kind, because there is strong
individuality in voices. This is due to the fact that structural
differences between the vocal tracts of individuals are far more
numerous and far more minute than possibly can be introduced into
instruments. Moreover, the vocal tract, being part of the human body,
is subtly responsive to innumerable impulses and adjusts and readjusts
itself in innumerable ways. Instruments are made of material, chiefly
wood and metal, and, unlike the vocal tract, cannot change structurally.
The cornet, for example, is made of brass. The lips of the player
protruding into the cup can effect certain changes in shape, and changes
also can be made in the tube between the mouthpiece and the bell of the
instrument by pistons or valves. But these changes are absurdly small
in number compared with the structural changes of which the vocal tract
is capable, and commonplace in character compared with the refined and
subtle minuteness of the latter. For this reason, while there is a
distinct timbre for each kind of instrument, there are innumerable
timbres of the human voice--as many as there are voices, and all due
to the pliability of the vocal tract.

It is the manner in which the numerous individual conformations of
the vocal tract affect the overtones in the voice that makes voices
different from each other; for the overtones are the chief agency in
determining the timbre, quality, or physiognomy of any tone. Every
tone consists of a fundamental or ground tone with its overtones. The
fundamental tone determines the pitch; the overtones determine the
quality, tone-color, timbre, or physiognomy of the tone.

The overtones, or harmonics, as they also are called, vibrate in certain
simple harmonic relations with the fundam