Rock Anthem for Saving the World
From Halopedia, the Halo wiki
Rock Anthem for Saving the World is the sixteenth track in Halo: Original Soundtrack.
The track features the triplet rhythm from the Halo Theme, accompanied by an electric guitar playing improvisations over the triplet rhythm. The piece was arranged into Rock in a Hard Place in Halo: Combat Evolved Anniversary: Original Soundtrack.
It can be heard: