What follows me from some time already is the idea of music version of a "horror game" of sort. In computer and even board games, you quite often have a general emotional aura of some kind of threat. The closest to that direction so far I've seen in music games is "Attack of the rhythm dancer" but that's a quite heavy game (for musicians) and I would think "game of emergence" (simple rules for complex interactions) that could go with a green face in our library.
There should be many ideas that fit that from music (silent, weird sounds and sudden loud sounds like in every horror soundtrack ;) ), games (trust and betrayal, I like e.g. Avalon of that type) and maybe helpful arrangements like darkness in a room.;) but I can't put any testable form together.
Tomorrow I hope to test a final version of "Agents" game which was a bit around the idea of "music game of mistrust" (but no sound effects). I'll put it in a library if it works, but horror should be more.
If anyone have some traces or directions to share, please.