From Halopedia, the Halo wiki
It starts with a low brass reorchestration of Enough Dead Heroes, then swells into a resonating melody. This is dramatically replaced by marching snare drums. High vocals then joins in with a soft melody. The piece then transitions into a fragmented and more minor choir melody, with several discordant notes being played in the background. The choir swells into an abrupt end before the piece once again takes a peaceful upturn, featuring a partial reprise of the Enough Dead Heroes motif with orchestral instruments.