Finish the Fight

Finish the Fight is the thirty-first track (Disc 2 Track 16) included in Halo 3: Original Soundtrack, and plays during the Halo 3 announcement trailer.

Overview
The piece begins with a piano chord of eighths. Choir joins in with a soft melody, then piano plays another, louder chord. The choir then "replies" with another louder variation of their melody. The piano plays again, then the orchestra joins in, swelling louder and louder. Suddenly, it quiets again for a fanfare with a five-note E Dorian melody in piano.

Strings then repeat the motif, reverting to Halo Theme's triplet melody of strings, choir, and brass that is centered around the chord of E Minor. This section is more of a "multi-melody", where each instrument has their own melody. The result is an extremely complex binding of all the melodies together. At the end, brass and strings play the piano theme again, while the choir joins the harmony. All instruments then play the five-note E Dorian melody triumphantly before swelling to a climatic ending.

Arrangements
While Finish the Fight was arranged into This is the Hour to match the in-game cutscene, the five-note E Dorian fanfare was adopted by various musical instruments in different instances of Halo 3, and made appearances in the following tracks:
 * Luck
 * Three Gates
 * One Final Effort
 * Gravemind
 * Keep What You Steal

The fanfare has since appeared in every mainline game in the series following Halo 3. The fanfare's melody first briefly appeared in Old Friend (in Finale from Halo 3: ODST Original Soundtrack). The melody then appeared in Say the Words (in The Package from Halo: Reach Original Soundtrack) as a reprise of Keep What You Steal. 343 Industries' composer Kazuma Jinnouchi then incorporated brief reprises of the melody in the tracks Atonement (from Halo 4: Original Soundtrack) and Blue Team (from Halo 5: Guardians Original Soundtrack). These were followed by the full fanfare being featured prominently in the Halo Infinite announcement trailer as well as the pre-release track Set a Fire in Your Heart. In the final release of Halo Infinite, the melody is sung by the choir in Zeta Halo, as a a part of the Halo Infinite's rendition of the Halo Theme.

Production notes

 * The five-note E Dorian fanfare was inspired by the chord progression in the piece Respite from Halo 2: Original Soundtrack. When composing the track, Martin O'Donnell was worried if the audience would find the five-note fanfare "over-the-top" or "too emotional". According to O'Donnell, members of the Microsoft marketing team laughed when they first heard the fanfare.
 * Martin O'Donnell intentionally omitted the use of Gregorian chant in the track, and instead relied on E Dorian key as an indicator of the trailer being related to Halo.
 * In Halo 3 ViDoc: Finish the Fight, Martin O'Donnell said he does not know whether the fanfare would make a reappearance after Halo 3. The five-note E Dorian piano melody then appeared in every mainline game in the series following Halo 3, being the only other melody featured in the games as frequently as the Halo Theme.