It’s a computational notebook, where all cells are running all the time. Fascinatingly, the UI is the code, adorned with small widgets. I think legibility could be improved for other users, but this points to possibilities in other domains.
@iamwil super cool! What’s the name of that software? I think I once encountered some tool where music could be programmed,,but way less sophisticated than this!
Strudel REPL

Strudel is a music live coding environment for the browser, porting the TidalCycles pattern language to JavaScript.