Portal 2 – Cheats

After you beat the single player campaign, you unlock a new title screen.

After you make your way through the game and start to interact with lasers you will come to test chamber 16/22. After entering the chamber and going through the door you will notice a turret to your right that is behind a wire mesh. Use the laser and cube in the test chamber to manipulate the laser to destroy that turret and the wire mesh will be blown away. Go inside this room and look down. You will see four musical turrets and one turret conducting the musical.