In 1967 Steve Reich discovered phasing: take two performers playing the same short repeating pattern in unison, then let one speed up almost imperceptibly. The two copies slide apart, moving through every rhythmic relationship, until the faster one has gained exactly one full pattern-length — and they snap back into unison.
Here each loop is a phase θ that runs from 0 to 1 and wraps. The driven copy runs at a rate δ faster, so the gap between them — the phase offset — drifts steadily around the cycle. The time for one full lap is the loop length divided by δ, which is also the period of the slow acoustic beating you hear.
This is minimalism's deep idea: the music is the audible process. Nothing is hidden in the composer's calculations — you can hear exactly which alignment you're in and follow the transformation step by step.
Flick the right wheel to set it drifting; scrub the dial to freeze any alignment and study the interlock.
Something in the simulation stopped unexpectedly — the lesson continues without it. Nothing you did was wrong; you can move on.