Behold a Pale Horse
From Halopedia, the Halo wiki
Behold a Pale Horse is an extremely diverse song included in the Halo 3: Original Soundtrack. It plays during the level The Ark.
It starts with a steady strings beat, joined later by a piccolo melody-variation of the choir chant from the Halo Theme. This is followed by a repetition by choir, which is in turn followed by a strings melody. Suddenly, the strings stop, and a brass melody starts. This is joined by more strings, and the whole thing starts to sound a little like the Halo Theme. A more peaceful section follows, mainly played by strings. At 3:10, a mysterious-sounding melody starts. Drums join in, and the motif repeats. Gradually, the section becomes more minor and gloomy, yet with a faint air of hopefulness about it.
At 5:00, a rapid melody starts, much more stimulating then the previous sections. It is based mostly off of the Halo Theme, with strings, drums, and choir. The melody continues for thirty seconds, then suddenly stops.
The name of the song refers to the Halo 1 song On a Pale Horse, a remake of which is played near the beginning.
It runs for 5:39.
