What is a polyrhythm?
A polyrhythm is two or more rhythms sounding at once that divide the same stretch of time into different numbers of equal parts. In 3:2 one voice plays three even notes while another plays two in exactly the same span; they meet on the first note and nowhere else until the span repeats. Every polyrhythm is a ratio, and the smaller the numbers, the more familiar it sounds: 3:2 is the swing of a waltz against a march and the engine of most West African and Afro-Cuban music; 4:3 is Chopin's right hand against his left; 5:4 and 7:4 are where things start to feel genuinely new.
Three near-neighbours are worth separating. A hemiola is 3:2 at the level of the bar: two bars of 3/4 heard as three bars of 2/4, the trick behind Bernstein's "America". A cross-rhythm is a polyrhythm used as the fabric of a whole piece rather than a passing effect, the term musicologists prefer for African drumming. And a polymeter is something else: rhythms that share the same pulse but have different lengths, so they drift apart and meet again bars later; that belongs to the drum metronome, and we come back to it below.
How the dial works
Each ring is one rhythm. The dial's full revolution is one cycle, set in beats of the tempo; every ring divides that cycle into its own number of equal steps, drawn as dots. The needle sweeps once per cycle, and a dot flashes as it sounds. Tap a dot to cycle it between accent, normal and mute; tap a track to select its ring and edit it in the card below: steps, pitch, level and sound.
The cycle length decides what "the beat" is. With a 4-beat cycle, a 4-step ring clicks the quarter notes and a 3-step ring plays three across them, 4:3 with the four on the beat. Make the cycle 3 beats instead and the roles swap: three clicks the beat and four crosses it. The presets choose the cycle so the slower ring sits on the beat, which is how the ratio is usually written. Rings are pitched apart (a fifth and an octave by default) because two identical clicks fuse into one lumpy line; with distinct pitches you can follow either voice, or the composite, at will.
How to count 3:2
The reliable method for any polyrhythm is the common grid: find the smallest count that both rhythms divide evenly, write out where each one lands, and read the composite. For 3:2 that count is six. The three-side lands on 1, 3 and 5; the two-side on 1 and 4:
| Count | 1 | 2 | 3 | 4 | 5 | 6 |
|---|---|---|---|---|---|---|
| Three | ● | ● | ● | |||
| Two | ● | ● | ||||
| Together | both | 3 | 2 | 3 |
Say "nice cup of tea" over the six counts: nice is both hands, cup the three-side, of the two-side, tea the three-side again. Set the metronome to 3:2 with a slow tempo, tap the composite on your knee until it is automatic, then split it: right hand on the three, left on the two. The counting grid under the dial draws exactly this for whatever ratio you have loaded, and marks the counts where the rings coincide.
How to count 4:3
Four against three needs a grid of twelve. The four-side lands on 1, 4, 7 and 10; the three-side on 1, 5 and 9. The composite (1, 4, 5, 7, 9, 10) is the rhythm of "pass the gol-den but-ter": pass together, then the sides alternate the (four), gol (three), den (four), but (three), ter (four). Notice the shape: two hits close together, a gap, two close together, a gap. Once you hear that lopsided pairing you no longer need to count to twelve; you feel the pattern and let the metronome confirm it.
Chopin's Fantaisie-Impromptu is the famous case, sixteenths in the right hand against triplets in the left, 4:3 for pages at a time, and Debussy's first Arabesque does the reverse, triplets over duplets. Jazz drummers use the same ratio the other way round, superimposing a slow three over the band's four.
5:4, 7:4 and beyond
Larger ratios are counted the same way, but the grids get long (twenty for 5:4, twenty-eight for 7:4) and past a point you stop counting and start hearing. Two tricks help. First, mute the ring you are supposed to play and keep tapping it while only the other one sounds; un-mute to check yourself. Second, accent the first dot of the faster ring only and listen for how the other ring's hits fall "just before" or "just after" it: 5:4 has a characteristic slow drift where the five seems to pull ahead of the four through the cycle and snap back at the top. Three-ring presets (4:3:2, 5:4:3) are best learned as two two-ring problems first.
A practice routine that works
- Pick a preset and slow it down: 60 BPM or less until the composite is comfortable.
- Tap the composite with one hand on your leg while both rings sound. Say the mnemonic if there is one.
- Split the hands: right on the outer ring, left on the inner. Keep the accented downbeat as your anchor.
- Mute one ring and keep playing it silently against the other. Un-mute to check; repeat with the other ring muted.
- Move the accent to a different dot, or mute a dot, so the pattern stops being a loop you have memorised and becomes a grid you can navigate.
- Raise the tempo in small steps, four BPM at a time, and go back down the moment the composite gets lumpy. The speed trainer automates exactly this ramp on the plain metronome.
- Change instruments: hands, then feet, then hand and foot, then a real instrument playing one voice against the metronome's other ring.
Polyrhythms in real music
- West African and Afro-Cuban traditions build whole grooves on three against two: a bell pattern in a compound 12/8 feel against a duple pulse, with every part placing itself relative to that cross-rhythm.
- Renaissance and Baroque dances, the courante especially, lean on the hemiola, and Brahms made it a fingerprint of his style two centuries later.
- Chopin's Fantaisie-Impromptu is the textbook 4:3; Debussy's Arabesque No. 1 the textbook 2:3 (or 3:2, depending on which hand you call the beat).
- Jazz drummers from Elvin Jones onward superimpose slow threes over fast fours, and soloists phrase in five or seven across the bar.
- Progressive rock and metal (Tool, King Crimson, Meshuggah) are usually polymetric: odd-length riffs riding over a steady 4/4. The next section explains the difference.
Polyrhythm vs. polymeter
Both put "more than one rhythm at once" in front of the listener, and they are often confused, but they are built differently. In a polyrhythm the parts agree on the cycle and disagree on how to divide it: 3 and 2 both fit exactly into one bar, so the pattern repeats every bar. In a polymeter the parts agree on the pulse and disagree on the length: a seven-note pattern of eighths against a 4/4 drum beat lines up with the downbeat only every seven bars, and in between the two drift past each other: the shifting, never-quite-repeating quality of a Meshuggah riff. A polyrhythm is a ratio of speeds; a polymeter is a ratio of lengths. This page does the first; the drum metronome, with its per-track loop lengths, does the second.
Why the rings never drift
Each ring's hits are placed on an absolute grid computed from the shared cycle start, cycleStart + cycleLength × step ÷ steps, rather than by counting intervals, so there is no accumulated error between rings, ever. Change the tempo while it runs and the cycle anchor moves to preserve the current phase, so the dial neither restarts nor jumps. It is the same design as the native engine in the Beatmate Android app, running here on the browser's audio thread.
Frequently asked questions
What is a polyrhythm, in one sentence?
Two or more rhythms that divide the same span of time into different numbers of equal parts and sound at once (three notes against two, four against three), so their hits coincide only at the start of each cycle.
Is 3:2 the same as 2:3?
They are the same composite rhythm; the difference is which side you treat as the beat. This metronome writes the ratio outer ring first, and the cycle length decides what the beat is: with a 2-beat cycle a 2-step ring clicks the beat and 3 crosses it; with a 3-beat cycle the roles swap.
What is the difference between a polyrhythm and a polymeter?
In a polyrhythm the rhythms share the same cycle and divide it differently (3 and 2 both fit exactly into one bar). In a polymeter the rhythms share the same pulse but have different lengths (a 7-note pattern over a 4/4 drum beat), so they drift apart and realign only after several bars. Beatmate’s drum metronome does polymeter; this page does polyrhythm.
Why does each ring have a different pitch?
With identical clicks the ear fuses two rhythms into one lumpy line. A fifth or an octave between them lets you follow either one, or the composite, at will. Presets place the base ring at the click’s own pitch and the others a fifth and an octave above.
What tempo should I practice polyrhythms at?
Slow enough that you can count the common grid out loud: for 3:2 around 60 BPM on the 2-beat cycle, for 4:3 around 50-60, for 5:4 slower still. Speed is the last thing to add: once the shape is in your hands it survives any tempo.
Can I play more than four rhythms at once?
Four rings is the limit here and in the app. Beyond that the composite is dense enough that the ear hears texture rather than rhythm, and no notated music asks for it.
How exact is the timing between the rings?
Every hit is placed at an absolute sample position computed from the shared cycle start, so the rings can never drift against each other; the only rounding is to the nearest sample (about 0.02 ms). Tempo changes move the anchor while preserving the current phase, so the cycle never jumps.
Can I save a polyrhythm?
Your current rings, pitches, cycle and tempo are remembered in this browser, and the share button copies a link that reopens exactly this setup. Named libraries of polyrhythms live in the Beatmate app.