e entire world of sense,
and is a parallel method of expression of the underlying substance,
or will. The world of sound is certainly capable of infinite variety
and, were our sense developed, of infinite extensions; and it has as
much as the world of matter the power to interest us and to stir our
emotions. It was therefore potentially as full of meaning. But it has
proved the less serviceable and constant apparition; and, therefore,
music, which builds with its materials, while the purest and most
impressive of the arts, is the least human and instructive of them.

The pleasantness of sounds has a simple physical basis. All
sensations are pleasant only between certain limits of intensity; but
the ear can discriminate easily between noises, that in themselves
are uninteresting, if not annoying, and notes, which have an
unmistakable charm. A sound is a note if the pulsations of the air
by which it is produced recur at regular intervals. If there is no
regular recurrence of waves, it is a noise. The rapidity of these
regular beats determines the pitch of tones. That quality or
_timbre_ by which one sound is distinguished from another of the
same pitch and intensity is due to the different complications of
waves in the air; the ability to discriminate the various waves in the
vibrating air is, therefore, the condition of our finding music in it;
for every wave has its period, and what we call a noise is a
complication of notes too complex for our organs or our attention
to decipher.

We find here, at the very threshold of our subject, a clear instance
of a conflict of principles which appears everywhere in aesthetics,
and is the source and explanation of many conflicts of taste. Since
a note is heard when a set of regular vibrations can be
discriminated in the chaos of sound, it appears that the perception
and value of this artistic element depends on abstraction, on the
omission from the field of attention, of all the elements which do
not conform to a simple law. This may be called the principle of
purity. But if it were, the only principle at work, there would be no
music more beautiful than the tone of a tuning-fork. Such sounds,
although delightful perhaps to a child, are soon tedious. The
principle of purity must make some compromise with another
principle, which we may call that of interest. The object must have
enough variety and expression to hold our attention for a while,
and to stir our nature widely.

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