On a Pale Horse
From Halopedia, the Halo wiki
Not to be confused with Behold a Pale Horse.
On a Pale Horse is the nineteenth track in Halo: Original Soundtrack.
The soundtrack begins with driving staccato notes from the high strings joined by pizzicato from the low strings in what can be guessed is an alternating time signature between 6/4 and 4/4 time. At various times, sections of the high strings voice themes and variations on the Halo Theme Gregorian chant, eventually developing a unique melody. At about a minute into the soundtrack, the strings start a sort of "call - answer" theme again divided by low and high strings, then reverts to the staccato theme this time voiced in the lower register while the higher register plays slow chords while they crescendo to the end of the soundtrack.
It can be heard:
The track was arranged into the following: