I made an ambient drone piece Harmonic Protocol. It is a feedback process, with filters that analyze the sound according to the 12-tone equal temperament scale, and amplifies those components that are 7 semitones away (modulo octaves). The result is a smooth drone that changes over time.
Prototyped with clive and extracted to a standalone C application using SDL2 for audio, which has the advantage of being able to be compiled by emscripten for web audio APIs to run in the browser. Source code on the page.
Future ideas: maybe try a 53-tone equal temperament version, though the CPU load will be approximately 4.5 times higher, and the web version already uses 15% of a core in Firefox (standalone version uses much less).