Three Gates
From Halopedia, the Halo wiki
200px Three Gates is a song included in the Halo 3: Original Soundtrack. It can be heard during the level The Covenant and is the first movement of the Covenant Suite.
It starts with a low strings note, which is followed by the piano melody from the Halo 3 Announcement Trailer. Next comes the beginning melody of the Halo 3 E3 2007 Trailer. At around 0:45, drums take over with a melody. Strings continue to play an accompaniment in the background. At 2:00, drums play a loud note, and the song Leonidas from Delta Halo Suite begins to play. Choir and strings are the main melody. This section is played at checkpoint Alpha on the Halo 3 level, The Covenant during the first hornet battle.
It runs for 4:35. Template:Halo Music