I mentioned my use of the Diablo soundtrack in a recent gaming session report. I find few things creepier than a music box. So coming across this track on Youtube was fortuitous. There may be a creepier music box track out there, but this one has its own unique menace.
And here is a classic music box track, from "For A Few Dollars More." The great thing about music box tracks are that as the music slows down, the tension builds.
And finally, here's a music box track that is probably too familiar ... the Davy Jones / Calypso theme from Pirates of the Caribbean. More wistful than scary, though I think it could be used to amp up the tension by having it be a trap that must be disarmed, otherwise it springs once the music stops.
One idea would be to have a trapped music box where there are three dials, each with the letters A-Z on them. You need to spell the word "BOX" with the dials, and press the stop button before the music ends. Seems simple, but will players figure it out, with the music playing in the background, and the clock ticking down?