French say, the timbre of a stop, has, in the course of this
book, been used on almost every page to designate the
characteristic difference of the oral effects of the various
stops; a further definition may therefore not seem ill-
placed. Even if we only compare the Oboe with the Flute,
or the Trumpet with the Violoncello, we shall see that,
although tuned to the same pitch, they cannot be mistaken
for one another, on account of the difference in their Tone
Colour. The expression " Tone Colour " has been used by
Helmholtz, the greatest authority on acoustics of any age,
in his " Sensations of Tone," and has thereby, in the ter-
minology of musical science, become classical. (Compare
Melde's "Acoustics," p. 345.) Tyndall owns that the Eng-
lish language has no equivalent, and he therefore envies
the German language the suppleness with which it adapts
itself to the requirements of nature. It is well known that
colour also depends upon the velocity of vibrations, so
that, for example, a blue light has the same relation to a
red one as a high note has to a low one. Tyndall felici-
tously compares any one single colour, which has a simple
ratio of vibration, with a tone, the vibrations of which
cannot be divided into simpler ones (every tone, the
vibrations of which have a complicated form, such as a
string, must be capable of being divided into a number
of simple tones, all of which belong to the harmonic scale
[1, 2, 3, 4, 5, 6], Compare Blaserna's " Theory of Sound,"
p. 200) ; while a mixed colour corresponds to a sound,
for the production of which the foundation tone and the
characteristic harmonics act together. Hence the expres-
sion " Tone Colour." In my article on Geigenprincipal, I
have made practical use of this theory, by the aid of which
Helmholtz explains the violin-like colour of this stop.
