Overview
Illustration and video showing how to play the tune from the 8-track tape in the piano in the music room.
Solution
Once you have the 8-track tape (track 4) playing through the broadcasting room, a series of notes will keep playing through the hallways. You need to go into the music room and play the same notes on the piano.
There are seven functional keys on the piano. I have labelled them, from left to right, 1-7.
The tune is 2-3-2-7-7-6-5-3-2.
Press the respective keys in order and you should be able to open the birdcage. If you make a mistake, you can just start from 2 again.