It's called Ascension by composer Neal Acree, featuring The Skywalker Symphony and Chorus, and vocalist Laurie Ann Haus.
Neal Acree has released the full track on his Youtube page:
I stumbled upon this a few days ago. I hope you're still around to enjoy it!
Moonstones and Money pickups are shared with all players in co-op. As for ammo, when you pick up ammo of a type you're full on, it will be transferred to another person, except for rocket ammo and grenades, which cannot be picked up if you're full on them. Everything else is per-player.
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That would be Black Dragon by The Vines.