From Halopedia, the Halo wiki
Halo Reborn is the twenty-second track (Disc 2 Track 7) included in Halo 3: Original Soundtrack, and plays in the Halo 3 campaign level Halo. It is composed of Halo Reborn (0:00-2:46) and Guilt and Punishment (2:46-3:59).
Halo Reborn (2:46) begins with mournful vocals accompanied by some minor electronic sounds. The vocals sing the melody of Under Cover of Night (from Halo: Original Soundtrack). The first section plays in the opening cutscene as John-117, Cortana, and Thel 'Vadam travel to Installation 08, and continues into the opening gameplay sequence in the snowy canyon. It also plays in Halo: Last One Standing when S. Hartley acquires John-117's signal. The piece made a short reprise in in the piece Reborn Relic (from Finale in Halo 3: ODST Original Soundtrack). In the second section, strings take over and build tension as vocals join in the background. The digital notes from the earlier track Infiltrate return in a reprise, but accompanied with a much more prominent percussion accompaniment. The piece fades out quickly. This section plays when Flood combat forms arrive on the installation in Flood dispersal pods.
Guilt and Punishment
Guilt and Punishment (1:13) takes over with an eerie ambiance and digital chimes before being joined by the intense, electrically-generated siren-like sounds from the track Shadows (from Halo: Original Soundtrack). The piece ends abruptly on a jarring violin chord. The ambiance plays when John-117, 'Vadam, and Avery Johnson enter the control room, and continues into the cutscene in which 343 Guilty Spark attacks the trio. The following siren-like sounds play during the gameplay sequence in which John-117 battles 343 Guilty Spark, with the jarring chord playing when John-117 lands the killing blow on Spark.