Sand particles self-organize into standing-wave nodal patterns on a vibrating plate as frequency changes. Each grain is pushed by the gradient of a rectangular-plate Chladni eigenfunction f(x,y)=cos(nπx)cos(mπy)-cos(mπx)cos(nπy), settling at the quiet nodal lines while jitter proportional to local vibration amplitude keeps grains bouncing near antinodes. 6,000 additively-blended point sprites simulate the sand.