Four pendulums and a pen: two frequencies per axis, decaying, and the figure they trace is a Lissajous curve slowly spiralling into its own centre — a Victorian parlour instrument that draws the ratio between two notes; the ratios are read from the spectrum so a chord has a shape.
Drawn with: a WebGL2 shader.
Reacts to and looks like: gpu, webgl2 and audio-reactive.
Family: Visualiser.
Runs in your browser. The preview above is the same program the renderer uses.