admit that both may be true--but
in different compositions. That is, it is frequently
impossible to tell whether a composition that is being
listened to is in two-beat, or in four-beat measure; and yet
it _is_ sometimes possible so to discriminate. Since, however,
one cannot in the majority of cases distinguish between
two-beat and four-beat measures, it will probably be best to
leave the original classification intact and regard four-beat
measure as a compound variety.

[Footnote 23: Pearse--Rudiments of Musical Knowledge, p. 37.]

100. The _commonest varieties of measure_ are:

1. _Duple_ (sometimes called even measure, or even time), in
which there are two beats, the first one being accented.
Examples of duple measure are 2/4, 2/8, 2/2, two-quarter,[24]
two-eighth, and two-half measure, respectively.

[Footnote 24: For explanation of terminology, see p. 48, Sec.
106.]

2. _Triple_, (the old perfect measure), in which there are
three beats, the first one being accented, the second and
third unaccented. Examples are 3/8, 3/4, 3/2, three-eighth,
three-quarter, and three-half measure, respectively.

3. _Quadruple_, in which there are four beats, the first and
third being accented (primary accent on _one_, secondary
accent on _three_), the second and fourth unaccented. (See
note above, under Sec. 99.)

4. _Sextuple_, in which there are six beats, the first and
fourth being accented, the others not. In rapid tempi this is
always taken as compound duple measure, a dotted quarter note
having a beat. It will be noted that the two measures
[Illustration] are identical in effect with [Illustration].

101. Other varieties of measure sometimes found are 9/8 and 12/8, but
these are practically always taken as three-beat and four-beat measures
respectively, being equivalent to these if each group of three tones is
thought of as a triplet. [Illustration] is identical in effect with
[Illustration].

102. _Quintuple_ (five-beat) and _septuple_ (seven-beat) measures are
occasionally met with, but these are rare and will always be sporadic.
The five-beat measure is taken as a combination of three and two, or of
two and three (sometimes a mixture of both in the same composition),
while the seven-beat measure is taken in groups of four and three, or
of three and four.

103. The sign [common-t