the syntonic comma pump. four familiar chords — C, A minor, D minor, G — each tuned purely from a note the previous chord leaves behind. no voice ever moves by anything but a pure interval, yet every time the progression comes home, home has sunk by 81/80 — a syntonic comma, 21.5 cents. escher's staircase is an illusion; this one really descends. about 56 cycles to fall a full octave. reverse to climb, temper to stand still.
click the canvas to start · gold bars are notes held over from the previous chord — the pure links the comma sneaks through