From polyrhythms to musical intervals

How does a polyrhythm become an interval?

A 3:2 polyrhythm combines three pulses in one voice with two in another over the same cycle. Speeding up both voices together preserves their ratio. When the repetition becomes fast enough, we hear pitches: a 3:2 frequency ratio forms a perfect fifth.

For example, voices at 220 and 330 Hz form a fifth. The “Rhythm → Interval” slider continuously speeds up the pulse trains, without substituting a recording for the rhythm.

Try it in three steps

1. Choose Polyrhythm mode and a ratio, such as 3:2. Press Start.
2. Gradually move “Rhythm → Interval” to the right, or tap “Hear the interval” to jump directly to the pitch range.
3. Return to “Rhythm ×1”. Mute a voice with A or B, then turn it back on to compare the two pulses.

Which intervals can you hear?

These intervals use whole-number ratios, known as just intonation. They can differ slightly from the intervals of an equal-tempered piano. The perceptual transition from rhythm to pitch is gradual and depends on the sound and the listener.

What about three rhythms?

Add voice C to play three rhythms at once, such as 5:2:4. The Triads family also offers major, minor, diminished, augmented, sus2 and sus4 chords. For example, the proportions 4:5:6 produce a major chord in just intonation.

A tool for practice and understanding

Keep one voice as a reference and clap the other rhythm. Then speed up to hear the corresponding interval. The metronome also offers tap tempo, subdivisions, swing and shareable favorites, so an exercise can move from a lesson to your own practice.