Four loops at different tempos and different lengths, playing at the same time. They line up at the start, then drift apart, then eventually meet again. Steve Reich did this with tape in 1968. Web Audio does it in your tab now.
KEY
MASTER TEMPO · 90 BPM scale
All four rivers start together. Press FLOW. They drift. They meet again at the master cycle marker.
How four rivers phase
Each river has its own tempo (in BPM) and its own loop length (in beats). At the start they all line up. Once the music starts, each river plays its loop independently. A 5-beat loop at 80 BPM repeats every 3.75 seconds. A 7-beat loop at 110 BPM repeats every 3.82 seconds. They drift slowly and only line up again at the master cycle — the least common multiple of all four loop durations.
The default rivers were chosen so the master cycle is several minutes long: 4 beats @ 70, 5 beats @ 88, 7 beats @ 110, 6 beats @ 132. Listen for two or three minutes and you'll hear chords, near-misses, and unexpected unison hits as the streams cross.
Each river is a 4-voice synth: detuned sine fundamentals with a fast attack and ~1.5s decay. River colors: flame, rose, sky, mint. Active beat lights as a glowing dot on the rotating ring.
Mute a river by clicking its row. Unmute by clicking again. SYNC restarts all four rivers from beat zero so they line up again.
