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: CE, starting with Halo. The song is played near the underground Forerunner base on Halo, the part of the Silent Cartographer where the player comes to the Cartographer building for the first time, the Assault on the Control Room when wandering through the innards of Halo, the end of 343 Guilty Spark, near the end of the level Two Betrayals, at the start of the Final Run chapter, in Keyes, while inside the ship and while 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 in the level "Two Betrayals" on Halo: CE
 * This song was remixed into part of Heretic, Hero on the Halo 2: Original Soundtrack.
 * This song is quite similar to Drumrun also on the Halo: Original Soundtrack.