Sorry I didn't write more when I was online, I got off pretty shortly after that, I think.
Ran a couple quick tests and found a couple things just now:
1. Tabbing out of the game while the music's running will have the song finish, but not start the next one until I get back to the tab. (It's probably some powersaving thing in the browser, IDK.)
2. It stops for good after 3 (four?) songs even when I'm actively on the game's tab. However many songs there are, I mean, it didn't repeat any. Ticking and unticking the music toggle only toggles the wave audio, the music doesn't come back.