Chladni Plate

The key's plate from above, clamped at its centre, with sand on it: wherever the plate shakes harder than gravity the grains hop about, and they come to rest on the nodal lines, which stay still. The bow is drawn down across the edge at the dark bar; the two circles are fingertips resting on the figure's nodal lines. Each key is its own plate, with its own sand; tap the plate twice to sprinkle it afresh.

The nodal lines of the ten figures on this plate, lowest first, with each one's pitch over the plate's lowest mode. The figure the keys are cut for is framed; the one sounding now is filled.

The bow's stick and slip lock the plate onto one mode and make true harmonics of it, unlike the plate's own overtones (the markers). Shift the bow along the edge or lift the finger and watch the note jump to another mode's line.