A triplet is the most common type of rhythmic division, in which a beat is divided not into two (as usual) but into three equal parts. It is notated as a group of three notes under a slur with the number “3.” Triplet motion gives music fluidity, a circling, “rounded” quality — in contrast to the “square” duple division.
Triplets are the basis of many genres: they run through barcarolles and nocturnes, and create the characteristic “swaying” of the waltz and of jazz swing (where the beat is implicitly divided in a triplet way). The combination of triplet and duple motion (as in the “three against two” device) gives rise to polyrhythm. The triplet is an example of how a simple mathematical division of time becomes the source of an entirely new sense of motion and character in music.
