compound time
A time signature in which each beat is subdivided into three equal parts rather than two
In Depth
In compound time, the beat unit is a dotted note: in 6/8 time, each of the two main beats is a dotted crotchet divided into three quavers. Common compound signatures include 6/8 (two beats), 9/8 (three beats), and 12/8 (four beats). Compound time creates a lilting, rolling feel that is characteristic of jigs, barcarolles, and many types of dance music. The distinction between simple and compound time is fundamental to understanding rhythm and metre.
The famous confusion between 3/4 and 6/8 haunts music students: both have six quavers per bar, but 3/4 groups them in threes while 6/8 groups them in twos of three.