When shadow hands disappear at the end of a night while indoors (i.e., inside the purchasable home), the music box jingle continues to loop not only in the player home, but also in all other enterable structures in town. The sound also persists in other enterable areas including Cave Clefts, Mant Hills, and ruin entrances. The passage of time doesn't appear to stop the looped sound as well, as 2 days have passed between the start of the sound looping.
Lose sanity to the point of having shadow hands appear during the night. Enter an indoor area like the player home in town and wait for dawn to allow the shadow hands to disappear on their own--the music box sound should loop in most indoor areas at this point.