This one is a tough one to figure out. To get the sheet music you need to Get a key for a music box. You can get the key by solving the puzzle with the planet’s. Light the fire and line up Saturn – earth – moon. This allows you to open up the moon and get the key.
Now that you have the key, the question is, where is the lock? The lock is in a box downstairs in the lounge. In the room where there is a record player near the kitchen. Next to the save chair is a chest. Open it up with the key and the sheet music is inside.
make sure you have plenty of matches. Once you activate the music box a dozen ghosts appear and you might have a hard time dodging them all. Run up to the kitchen. The door that was once blocked up is now broken open and you can get out this way to go back upstairs.