Supercollider
supercollider.github.ioStrudel REPL is a browser-based music programming language based on Tidal Cycles which is based on Super Collider.
https://strudel.cc/ Strudel on HN: https://news.ycombinator.com/item?id=45571822
Worth mentioning the "supercollider-vscode" extension - makes Supercollider dev experience much smoother than it was a decade or so ago.