You must have the Annihilation DLC for this. You play this song by holding X (A on 360) when your near these small teddy bears. these teddy bears are standing up and holding large sickles. One is in the first room you appear in, its on the top level of the room on the right side next to a radio. The second is near the lunar lander next to the speed cola machine on a high ledge. And last is by the lunar lander nearest to stamin-up. On the left side of that part of the map there is a gate, you go to the gate, crouch, and somewhere behind the gate is another teddy bear. Once you hold X (A) to all 3, the song will play.