Ambient Wonder

Ambient Wonder is a song included in the Halo: Original Soundtrack. It plays during sections of the level Truth and Reconciliation.

Overview
It is defined by a constant, slowly modulating synthesizer tone approximating the sound of a jazz organ. At 00:14, a slight undertone of shifting higher notes begins to show under the synth melody. Over the next few minutes, these two parts blend and weave together to produce a soft, ambient piece reminiscent of (and based on) the main Halo theme.

It runs for 1:59.

Trivia
Oddly, 1+5+9 = 16 1+6 = 7 Seven is Bungie's favorite number, meaning this may be deliberate.