Gametrailers has a preview video (Part One, Part Two) of  Left4Dead 2′s “The Passing” DLC, which contained the following comment from Bret Faliszek, writer at Valve Software:

Not only do [sic] the Midnight Riders have a new song coming out in this game, in Rock Band, you’ll actually get to play the Midnight Riders, we’ve got some songs coming out there.

Who are the Midnight Riders?  They are a fictional band from the popular zombie co-op FPS series, Left 4 Dead.  In Left 4 Dead 2′s second chapter “Dark Carnival”, the heroes make their way through an abandoned amusement park to an empty concert amphitheater.   It seems that the Midnight Riders were due to perform a show minutes the zombie apocalypse began, but were instead helicoptered to safety.  The heroes try to summon the same helicopter by activating the stage’s sound system and fireworks show, which subsequently attracts every zombie for a hundred miles.  During this frenzied finale, two songs from the Midnight Riders are playing at full volume over the arena’s speaker system.

Valve has taken the promotion of this band to a viral level, publishing a blog for the band, and creating a YouTube channel.  Here are the tracks:

• Midnight Riders – “All I Want for Christmas (is to Kick Your Ass)”
• Midnight Riders – “Midnight Ride”
• Midnight Riders - “One Bad Man”

Mr. Faliszek did not say which tracks would be available for Rock Band 2, nor did he hint at a release date.  My best guess is that the songs will be the “New” yet-unreleased song from “The Passing” and the opening tracks to their record “High Heels and Brushed Steel“, and also that the songs will likely be released on the same day as the DLC for Left 4 Dead 2, sometime in late March 2010.

These will not be the first songs from other videogames to appear in Rock Band, as Jonathan Coulton’s “Still Alive” is from another Valve game called Portal.  When this rumor is confirmed by Harmonix I’ll post more information.