ist's
utterances or creations must be intelligible, and they must be
interesting. The lack, partial or total, of either of these qualities
neutralizes the force of the intended impression, in precise proportion
to the default.

In musical composition these two requisites are embodied in the
principles of Unity and Variety.

_Unity_--in its various technical phases of Uniformity, Regularity,
Similarity, Equality, Agreement, or whatever other synonym we may find
it convenient to use--is the condition out of which the composer must
secure intelligibility, clearness, definiteness of expression. Glance
at Ex. 2, and note the evidences of unity (similarity) in the rhythmic
and melodic formation of the first four measures.

_Variety_--in its most comprehensive application--is the medium he must
employ to arouse and sustain the hearer's interest. Glance again at
Ex. 2, and note the contrast between the two halves of the first four
measures, and between these and the following two measures.

These conditions are, of course, squarely opposed to each other, though
their interaction is reciprocal rather than antagonistic; and, from
what has been said, it is obvious that they are of equal importance.
Hence, as was declared on the second page, the great problem of the
art-creator consists in so balancing their operations that neither may
encroach upon the domain of the other. For too constant and palpable
Unity will inevitably paralyze interest; while too much Variety will as
surely tend to obscure the distinctness of the design.

* * * * * *

The workings of the principle of Unity (to which attention must first
be given, because it appears to come first in the order of creation)
are shown in the following elementary details of composition:--

(1) Music is not an art that deals with space, but with Time; therefore
the units of its metrical structure are not inches and the like, but
divisions of time, the basis of which is the _beat_. The principle of
Unity dictates that the beats which are associated in one and the same
musical sentence shall be of equal duration. Every musician admits the
necessity of keeping "strict time"--that is, marking the beats in
regular, equal pulses. The sub-divisions of the beats (for example,
the eighth or sixteenth notes within a beat) must also be symmetric.
So imperative is this law that it generally prevails through the entire
piece, with only such tempora