Compound meters · Rhythm and meter · Music theory
In a compound meter each beat divides into three: the beat is a dotted note. In 6/8, 9/8 and 12/8 the top number counts eighths, and the beats are a third…
Compound meters
In a compound meter each beat divides into three: the beat is a dotted note. In 6/8, 9/8 and 12/8 the top number counts eighths, and the beats are a third of that number: two, three and four dotted-quarter beats.
6/8 and 2/4 both have two beats, but they do not sound the same: in 6/8 each beat divides into three eighths; in 2/4, into two.
Equivalents and irregular meters
Each simple meter has its compound equivalent, with the same number of beats: a common exam question. The compound is found by multiplying the top number by three and the bottom by two.
Irregular meters combine unequal beats: 5/8 is 3+2 or 2+3 eighths, and 7/8, 2+2+3 in any order. The second movement of Tchaikovsky’s Pathétique Symphony, Holst’s Mars and Dave Brubeck’s Take Five are in 5/4.
The hemiola
A measure of 6/8 can also be grouped as three quarters, instead of two dotted quarters: the accent shifts and the meter seems to change without changing. It is called a hemiola, and is very typical of Baroque cadences and of many Spanish dances.