The relationship between additive and divisive rhythms is complex, and the terms are often used in imprecise ways. The seventh edition of the New Grove Dictionary of Music and Musicians, in its article on rhtyhm, states that "In discussions of rhythmic notation, practice or style, few terms are as confusing or as confusingly used as 'additive' and 'divisive'."
Most western music is primarily divisive, while Indian and some other musics are primarily additive. However, most pieces of music cannot be clearly labeled divisive or additive.
The term additive rhythm is also often used to refer to what are also called asymmetric rhythms - that is, metress which have a regular pattern of beats of uneven length. For example, the time signature 4/4 indicates each bar is eight quavers long, and has four beatss, each a crotchet (that is, two quavers) long. The asymmetric time signature 3+3+2/8, on the other hand, while also having eight quavers in a bar, divides them into three beats, the first three quavers long, the second three quavers long, and the last just two quavers long. These kinds of rhythms are used, for example, by Béla Bartók, who was influenced by similar rhtyhms in Bulgarian folk music, and in the music of Philip Glass's, and other minimalists, most noticably the "one-two-one-two-three" chorus parts in Einstein on the Beach. They may also occur in passing in pieces which are on the whole in conventional metres.