Sacrifice is the eighteenth track included in the Halo 4: Original Soundtrack Volume 2.
This piece is played during Prologue just before Dr. Halsey says "What are you after?...".
It also plays during the opening cutscene of Midnight and when UNSC Infinity blows a hole in Mantle's Approach to allow John-117 to enter the vessel in the same mission.
List of music heard in the Halo series