Planets on concentric orbits, each with its own period; every pass across the upward trigger ray plays that orbit's note. In harmonic mode the periods divide evenly — a strict 1:2:3:4… polyrhythm that drifts apart and realigns in a grand unison once per cycle. In phasing mode every orbit takes almost the same time, so identical pulses slip slowly out of sync and back — Steve Reich's tape phasing, as circular motion. Pitches stack scale-wise from the outermost (slow, low, loud) to the innermost (fast, high, soft).