From Halopedia, the Halo wiki
Alien Corridors is the fifteenth piece included in the Halo: Original Soundtrack.
The piece is dominated by a series of odd, atonal chimes, similar to the noises given off by Covenant holo-panels in the accompanying level, The Truth and Reconciliation. It can be heard when John-117 enters the cargo bay of the eponymous ship, and the name of the piece alludes to how the player must navigate through the Covenant ship which has many narrow corridors.
The piece starts off with the "alien chimes" alone, but at 00:09, an extremely high synth note begins to assert itself, giving shape and pattern to the chimes. Starting at 00:19, a series of drums start up, giving the piece a driving, yet irregular, beat. At 00:31, a crash of cymbals leads the piece into its main section, allowing the drumbeats to push the piece into a slightly frenetic pace as the high-pitched synth fades out.
At 00:40, an even higher-pitched synth note takes over where the last one left off; the chimes shift their pattern and become somewhat more minor. At 00:49, another cymbal note removes the synth and sets the piece pace forward again as the chimes sound over the pulsing drums. At 00:56, the drums mostly drop out, revealing a midrange synth note underlying the piece; shortly thereafter, the high synth returns to give the beatless piece a sense of shape.
The piece continues without drums; at 01:17, the synth is joined by high strings, which slowly cycle through chords that drown out the chimes. At 01:29 the chimes become briefly audible again as the high strings fade out to make way for lower strings that continue the chords. The piece gradually fades out with the mid-range strings alone.
The piece is remastered into Xenoarchaeology in the Halo: Combat Evolved Anniversary: Original Soundtrack.