The Halo 2: Original Soundtrack was composed and produced by Martin O'Donnell and Michael Salvatori, with a few tracks by Incubus. While the Halo: Original Soundtrack was released in a one volume format, the Halo 2: Original Soundtrack was split into two volumes, which were released almost two years apart. Volume 1 was released on November 9, 2004 and Volume 2 was released on April 25, 2006. Rather than keep the medley from the Halo: Original Soundtrack, the Halo 2: Original Soundtrack focused more on suites with different chapters, similar to movements in a symphony. Unlike the Halo: Original Soundtrack, the Halo 2: Original Soundtrack focuses more on heavy guitar riffs and beats as evident in the re-designed Halo Theme Mjolnir Mix. As such, O'Donnell brought in several bands and guitarists (such as Incubus and Breaking Benjamin) to help compose the songs.
Volume 2 of the soundtrack differs greatly from Volume 1 in the presentation and form of the songs. While Volume 1 is made up in a "movement" form, Volume 2 focuses heavily on suites. As stated on the Volume 2 inlay card, Martin O'Donnell details why he chose to use this structure: "I decided to use a "suite" structure that corresponds to the chapters within the game. In a sense, by listening to this soundtrack, you will hear the musical representation of the story of Halo 2."
- Volume 1 also included an excerpt of the Covenant Writ of Union.
- Volume 2 also included an excerpt of the Covenant Ratification Parley.
- When played in reverse, the "Destroyers Invocation" part of Mausoleum Suite on Volume 2 plays a cryptic message from what is thought to be the Gravemind.
- Halo 2 has the most unreleased soundtracks of all of the Halo soundtracks.
- This is the first Halo soundtrack to have 2 volumes.