Sand is scattered across a metal plate. A violin bow is drawn along its edge. The plate vibrates at a specific frequency — and the sand migrates away from the regions of maximum movement, settling into the lines where the plate is still. These lines are called nodal lines. The pattern they form is the shape of the sound. Different frequencies produce different geometries. Simple frequencies produce simple crosses and rings. Higher frequencies produce increasingly complex mandalas. The plate is drawing the sound in sand.