// write-up

Musical Spirograph

january 2026

Rotating circles trace geometric curves on canvas, and when the drawing arm crosses certain rings it triggers notes. The math is the classic epicycloid formula extended with multiple arms, so you can stack rotations to get increasingly wild patterns. Six presets (Classic, Flower, Star, Orbit, Lotus, Spiral) give you starting points, and you can tweak everything from there.

  • Epicycloid math with up to 3 arms for complex curves
  • Canvas rendering with a secondary trail layer
  • PolySynth through a compressor, limiter and reverb so stacked notes stay clean
  • Ring-crossing detection triggers notes from the selected scale
  • Note quantization (1/4, 1/8, 1/16) to keep things rhythmic
  • 6 sound types and 6 scales to choose from

Changelog

  • Cleaner audio after some kind words (and fair qualms) from The Verge and Gizmodo: a limiter, compressor and reverb, softer attacks, and quieter notes when lots play at once
  • Initial release