It's hard to overstate what an impression Halo made on its release, and a big part of it is the orchestral soundtrack. The choir singing the Halo theme is a unmistakable melody, and sure to be recognized by a lot of people.

While the other tracks are nice and atmospheric, they don't really linger..Basically any track that uses the choir instantly stands out above the other tracks.

With the exception of the "Truth and Reconciliation Suite", the tracks are pretty short, which is pretty unusable considering how long a level can be..the endless running through corridors and battles would benefit from a bit more diversity.. but the later Halo sequels address this with longer tracks.

When thinking about Halo's music you usually think of the classic Halo theme, but I have to mention "Under Cover of Night" here: a great track that I didn't remember but which really stood out during replaying the game.