In Chapter 2, you will need to do this to open a door and progress the game. After you have found heard Wally's log ad found his keys, there is an audio log in the closet. This will tell your four instruments to interact with in the Music Room. They change for each person, so I cannot list them. You need to go upstairs and turn on the projector, which will make ink monsters appear when you come back down. Now you need to go to the Music Room and do all four instruments before the cartoon ends. You can stand on the chair under the projector and aim up if you need more time to get all four instruments. The violin is on a chair, the piano is near the opening in the wall and the other instruments are on the stage.