The scariest games I’ve ever played have all been sessions of Dread. Let me tell you about our very first playtest of the game. We already had most of the rules there (plus a few extraneous bits that we thankfully dumped before we published), so it was pretty much what you’ve played if you’ve played Dread (though characters were pretty different). Eppy and I were playing in our kitchen with our friend Dan, with the lights low. Eppy was running the game. He had set up a playlist of mood music, looping on his computer a couple rooms away. We were dealing with some creepy cultists in a recently post-apocalyptic land. We had discovered they were engaging in human sacrifice and maybe cannibalism, and decided we needed to get away while we still could. Dan was working on a pull, his hand almost on the tower, and the music was so quiet as to be inaudible. Then, with no warning, an agonizing scream erupted from the next room. We all jumped a foot in the air, Eppy included, and had to take a break before Dan could finish his pull and we could continue the game. Sure, it was just a coincidence and a startle, but it wouldn’t’ve mattered if the game hadn’t been so scary to begin with, if we hadn’t all been so tense through the combination of the events in the game and that looming tower on the table.
I don’t think we ever bothered with music for a Dread game again—it was almost too much. But we continued to play and run scary sessions of Dread, and I’ve even seen it work its magic in loud, brightly-lit, crowded convention rooms.
Oh, that scream? It’s part of the opening of a Samhain song, which actually has some very soft other sound effects, but those were inaudible on computer speakers a room away. Unfortunately, neither Eppy nor I can remember the exact song, and some quick googling didn’t provide the answer.