About the music: Thin ice. If you pick the right ones, its okay but people mostly play games muted. If you pick the wrong one though... those who do play with sound will be pissed and will mute it but the bad impression will remain. I believe that if you don't wanna give music to the grim parts and instead focus on a general background music than its fine. Otherwise its mostly a choice between "adds nothing" and "annoyance". I've played a few games with fitting music which ment like 5 second of pleasant suprise but after that i cared and focused only on the game.
Here is my suggestion. The horror/violent elements are not represented best with actual music. Fastpaced violent music befits fightin scenes, action scenes. Horror, grim, gloom is best enhanced by certain (just for example)
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or creepy instrumental. But to give contrast i once posted a game's
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and it was unnerving to some for whatever reason and i guess that counts as eerie :coldsweat: The OST of VtM:Bloodlines is another good example: all the Creepy Ambience tracks, Moldy Old World, Luckee Star Motel, Dark Asia do serve their purposes well.