The Menagerie
From Halopedia, the Halo wiki
The Menagerie is a track from the Halo 3: ODST Original Soundtrack. It contains the smaller tracks Ground War, Oscar Mike, Unleashed, and On the Prowl.
A menagerie is a place in which a variety of usually exotic animals are kept.
The track takes place during the 2nd flashback, Uplift Reserve (Level), when you play as Dutch.