The Gun Pointed at the Head of the Universe

The Gun Pointed at the Head of the Universe is a piece included in the Halo: Original Soundtrack.

Appearances
It is heard in almost every level of Halo: Combat Evolved, starting with the level Halo. In Halo, the song is played near the underground Forerunner structure. In The Silent Cartographer, it plays when the player comes to the Silent Cartographer building for the first time. In the Assault on the Control Room level, it plays for a few seconds when you first enter a Scorpion, it plays when you encounter the tunnel entrance guarded by two Wraiths, and it also plays when you battle the Plasma Rifle-wielding Zealot Elite. In the 343 Guilty Spark level, it plays when you are defending the Forerunner building. In Two Betrayals, it plays at the start of the "Final Run" chapter. In the Keyes level, it plays when you first enter the shuttle bay immediately after Captain Keyes orders you to pull out. And in The Maw level, it plays while the Master Chief blows up the engines of the Pillar of Autumn.

Overview
It is composed nearly entirely of percussion, only having a deep bass note towards the middle of the piece and some vocals at the end of the piece. The rest of the sound is produced by a combination of drums, auxiliary percussion and hand-clapping, which is usually unheard of in many tracks written for Halo.

Trivia

 * The name of the song is most likely in reference to the Halo Installations, or the "Gun Pointed at the Head of the Universe". It plays multiple times in Halo: Combat Evolved; from the levels Halo to 343 Guilty Spark, where it is featured most prominently at the end of the level.
 * The name is also a chapter at the start of the level Two Betrayals in Halo: Combat Evolved.
 * This song was remixed into part of Heretic, Hero in the Halo 2: Original Soundtrack.
 * This song is quite similar to Drumrun also on the Halo: Original Soundtrack.