In music, additive meter refers to a pattern of beats that subdivide into smaller, irregular groups. This is opposed to "divisive" or "multiplicative" rhythms or meters, which are produced by multiplying some integer unit into regular groupings forming beats of equal length (London 2001). Such meters are sometimes called "imperfect", in contradistinction to "perfect meters" in which the bar is first divided into equal units (Read 1964,). Additive meter is common in Eastern European musics, and contemporary compositions attempting to emulate such a sound. For example, a time signature like 9/8 is normally subdivided as 3+3+3, or nine eighth notes with three to a beat. However, the composer or conductor may specify an additive meter for passages of music where it is more natural to conduct with a different pattern. Hence, a meter like 9/8 may instead be subdivided as 2+3+2+2 for musical effect; most commonly such an additive meter is used when accented notes or syncopated patterns do not match up with the normal subdivision.
Flamenco music, for instance, is full of additive meter, particularly in rhythms of 10 (3+3+2+2). Alfred Reed's Armenian Dances (Part I) contains a movement written in the nonstandard time signature of 5/8, which can be conducted as either 2+3 or 3+2 depending on which is more musically natural.