To get this achievement, you need to interact with the Music Box in the level Into the Closet (Level 4)
NOTE: This is not the Music Box in your room.
After you extend the first bridge, cross it and look to the right. Climb the box and table and get to the top. Once at the top, open the first door on your right. Inside you will see the Music Box. Go up to it and interact with it for the achievement.