r seven beats are grouped together. This involves a
mingling of the duple and triple species, and, consequently, an
irregular disposition of the accents; for instance, 5-4 measure is
either 3+2 or 2+3 beats, with corresponding accentuation:

[Illustration: Beat accentuation]

RHYTHM.--This word signifies arrangement,--a principle applied, in
music, to the distribution or arrangement of the tones according to
their various _time-values_. The system of measurement (or metric
system) furnishes tone material with all the details of division,
proportion and comparison; but this, alone, is not rhythm. The metric
system affords the basis for rational and definable rhythm, but
"rhythm" itself does not enter into the proposition until
differentiated factors are associated and opposed to each other.

[Illustration: Example 3. Rhythm.]

The first measure of this hymn is, by itself, merely an exponent of the
metric principle, for it consists of three uniform quarter-notes. The
second measure, however, is a rhythmic one, because, by dotting the
first of the three beats, three different time-values are obtained
(dotted quarter, eighth, and quarter). Further, by association and
comparison with each other, both measures assume a collective rhythmic
significance.

The rhythmic disposition of the tones is to a certain extent optional
with the composer, but by no means wholly so; the rules of rhythm are
probably the most definite and obvious of all the rules of music
writing. They do not concern the analytical student intimately, but at
least the general distinction between regular and irregular rhythm
should be understood:--We have seen that the natural accent (the
"heavy" pulse) is invariably represented by the first beat of a
rhythmic group; and that one or two lighter pulses intervene before the
next accent appears. Further, it is self-evident that the rhythmic
weight of a tone is proportionate to its length, or time-value; longer
tones produce heavier, and shorter tones lighter, impressions. The
deduction from these two facts is, then, that the rhythmic arrangement
is _regular_ when the comparatively longer tones occupy the accented
beats, or the accented fractions of the beats; and _irregular_ when
shorter tones occupy the accents, or when longer tones are shifted to
any comparatively lighter pulse of the measure or group.

The rhythm of the second measure in Ex. 3 is regular, because the
longest tone stands at the