Polyrhythm

What it means

Polyrhythm designates the simultaneous sounding of different rhythmic organizations. The simplest and best-known form is two against three: one voice divides the beat into two parts, another at the same time into three. Alongside this there are three against four and further ratios, increasingly difficult to coordinate.

In the notation

The phenomenon is recognizable by triplet, duplet, or other division numbers in one voice, while the other continues unchanged. The shared reference points are the beats at which both divisions meet; between them the notes of one voice lie between those of the other. To be distinguished from this is polymeter, in which different voices are notated in different time signatures and not even the metric accents coincide.

Musical use

The effect rests on the tension between two orders that both remain audible. In European art music it often appears at isolated points — as a duplet in a triple-metre flow, as a triplet against straight eighths — and there creates a brief floating. In the music of many non-European cultures, especially in West and Central African traditions, the simultaneous layering of different counting patterns is, by contrast, a constructive principle from which whole pieces are built; through this route it influenced jazz and popular music.

In twentieth-century music the procedure was considerably expanded, up to ratios that can only be determined computationally.

Common forms are three against two and four against three. In West African drumming music, several rhythmic layers constantly overlap.

Performance practice

Practise two against three by securing both layers separately first and then joining them very slowly; keep the shared beginning of the beat firmly as an anchor. Keep counting in the overarching unit, not in the subdivisions. Beware of assimilating one layer to the other — the appeal lies in both keeping their own character. And record yourself: inaccuracies are often not heard while playing.