DinoEvil, this is hard to explain so just bare with me - First off, have you got the Employee Elevator Key from room 204 from there stay on the same floor and go across the lobby landing to the other side of the hospital where you will see a big gray rectangle patch on your map and that is where the Employee Elevator is and from here it is quite easy to fin the final music box.
Hope i explained it clearly enough for you, if not say so and i'll try harder.