After getting past the room with the three men, there should be two more as you enter the room to your right and one man across the room to your left. This is the room with the music. Go upstairs to where you can look down on the music room (you should be able to launch fireworks). Go to the right side, towards the speakers. You may want to save the game here. Jump onto the ledge and then towards the speaker while moving left. There is Ingram ammo and more over there.