Rhythm & Groove — plain-language explainers

What rhythm and metre actually mean, definitionally

Britannica’s own entry on rhythm is more honest than most casual definitions: “rhythm, in music, is the placement of sounds in time, generally considered as an ordered alternation of contrasting elements,” and the same entry admits “attempts to define rhythm in music have produced much disagreement.” Metre is the more precisely defined half of the picture: “rhythmic pattern constituted by the grouping of basic temporal units, called beats, into regular measures, or bars.” A time signature states that grouping directly — the top number is beats per measure, the bottom is which note value counts as one beat — and Britannica sorts metres into two families: simple (duple, triple or quadruple — 2/4, 3/4, 4/4) and compound, where each beat itself divides into three (6/8, 9/8, 12/8).

Why “polyrhythm” and “polymeter” need two different words at all

Both devices below recombine that same simple/compound raw material, just in different directions. A polyrhythm layers a different beat-grouping within the same metre — the bar length stays fixed, but a rhythmic figure repeats on a cycle that does not match the beat. A polymeter layers different metres entirely — genuinely different bar lengths, running concurrently. That distinction is standard music-theory vocabulary applied to Britannica’s own metre definition above, not itself a sentence quoted from either entry — but it only makes sense once metre is defined precisely, which is exactly why this hub leads with the definition rather than the two named devices.

Same bar, or different bars: a rhythmic figure that repeats every three beats inside an ongoing 4/4 bar is one metre, displaced against itself — a polyrhythm. Two instruments playing in 4/4 and 3/4 at the same time are two of Britannica’s “regular measures” running side by side — a polymeter. One word describes tension inside a metre; the other describes two metres coexisting.

Polyrhythm or polymeter? Read the description against the definitions above

Pick the description closest to what you are hearing.

Where this comes from

Britannica — Rhythm, by Peter Crossley-Holland, updated 26 March 2026: the definition and the note on disagreement, quoted above. britannica.com · accessed 4 August 2026.

Britannica — Metre (music): the definition, the time-signature explanation, and the simple/compound distinction quoted above. britannica.com · accessed 4 August 2026.

The polyrhythm/polymeter distinction above is standard theory terminology applied to Britannica’s metre definition, not itself a claim quoted from that entry.