I feel really, really stupid for asking this. Actually, I’ve thought of asking this before but have chickened out.
Here it is.
The settings menu has volume in it. There’s no sound in the game, right? I’ve never heard sound.
SDL version has sound support, but you need to grab the music separately and add it to the data/sound folder. You can also add/change track listings in soundset.json (found in that folder) to have the game play whatever you want.
Dynamic music has not yet been implemented though. :-/