Asphalt and Ablution
From Halopedia, the Halo wiki
Asphalt and Ablution is the sixth track (Disc 1 Track 6) included in Halo 3: ODST Original Soundtrack, and plays in the Halo 3: ODST campaign level Mombasa Streets. It is composed of Still Grounded (0:00-1:44), Island of War (1:44-2:46), Hardboiled (2:46-4:24), and Sneaking Suspicion (4:24-6:04).
Still Grounded (1:44) begins with a short piano solo playing a slow and mysterious melody, soon joined by strings accompaniment as well as short woodwind cues echoing the piano melody. The melody repeats in different keys before ending with a solo phrase by the piano. The piece plays randomly in the main menu, and in the campaign level during the cutscene following Uplift Reserve, then continues into the gameplay sequence afterwards.
Island of War
Island of War (1:02) features percussive beats. The rhythm speeds up and grows more complicated as more instruments join, playing a heavy and quick melody. The piece plays randomly when roaming in Mombasa Streets.
Hardboiled (1:38) begins with a suspenseful piano melody, quickly joined by accompaniments from a tenor saxophone and muted percussion. As the piano melody repeats, the saxophone improvises with various melodies. The piece fade out. The piece plays randomly when roaming in Mombasa Streets, but its in-game version features a much longer improvisation section by the saxophone.
Sneaking Suspicion (1:40) features eerie ambiance which plays randomly when roaming in Mombasa Streets, but its in-game version is much longer.