Halo 3: Legendary Map Pack Preview: Blackout
The third map announced by Bungie for the Legendary Map Pack.
A simple remake of Halo 2's Lockout. Except this time it is set in some sort of a base in the arctic at midnight.
I believe this is the map Bungie called "Moonlight Sonata" before being officially announced.
The song is the Halo theme by Corporeal