Well, I'm trying to explain this without confusing you more... Or without giving away any secret plot I was hoping to pop in.
The 'Monsters' in this role-play are people who want to take away the music box, or kidnap the characters, or just do something terrible and unlawful in general.
The characters, however, do not live in haunted houses; though, most of the parents of characters (whom will be NPCs during the role-play) are skeptical about the music boxes, and don't believe that the characters' good luck charm or keep them protected; and lastly, no, everyone can see the music box, hear the music box, etc.~
I hoped I cleared up the confusion~