ne_, two, _three_,
four |--etc. Rhythm is thus seen to be a fundamental thing,
inherent in the music itself, while measure is to a certain
extent at least an arbitrary grouping which musicians have
adopted for practical purposes.

98. In _syncopation_ the normal system of accenting is temporarily
suspended and the accented tone falls on the regularly unaccented part
of the measure. Syncopation may therefore be defined as the temporary
interruption of a normal series of accents, _i.e._, accenting a beat
that is usually not accented. Thus _e.g._, in Fig. 56, measure _one_ has
the regular system of accents normally found in four-quarter-measure,
(strong accent on one, secondary accent on three); but measure _three_
has only one accent, and it falls on the second beat.

[Illustration: Fig. 56.]

99. Measures are usually classified as _simple_ and _compound_. A
_simple measure_ is one which has but a single accent, _i.e._, the
measure cannot be divided into smaller constituent groups. There are two
main classes of simple measures, two-beat measure, and three-beat
measure. A _compound measure_ is (as its name implies) one made up by
combining two or more simple measures, or by the elaboration of a single
measure (in slow tempo) into several constituent groups. The principal
compound measures are four-beat and six-beat, both being referred to as
compound-duple measures. Five-beat, seven-beat, nine-beat, and
twelve-beat measures are also classified as compound measures.

An English writer[23] classifies measures as duple, triple, or
quadruple, specifying that a simple measure is one in which
each beat is represented by a note whose value can be divided
into halves ([Illustration] etc.) and that a compound measure
is one in which each beat is represented by a dotted-note,
whose value can be divided into three parts, ([Illustration]).
There is thus seen to be considerable difference of opinion as
to the meaning of the words _simple_ and _compound_ when
applied in this connection, the principal question at issue
being whether four-beat measure is an individual variety, or
whether it is a variety compounded out of two-beat measures,
either by placing two of these in a group or by the
elaboration of a single measure into a larger number of beats,
as is often necessary in slow tempi. Perhaps the easiest way
out of the difficulty is to