Mjolnir Mix featuring guitar virtuoso Steve Vai will be available for free on Xbox Live Marketplace on Thanksgiving. 

Some Guitar Hero fans have been unhappy with the cost of downloadable songs for the series since its debut on the Xbox 360 earlier this year. Microsoft and Activision are set to silence those complaints for at least one day, as the pair announced that in appreciation to their fans, they will offer the "Mjolnir Mix" of the Halo theme song as a free downloadable track for Guitar Hero III: Legends of Rock on Thanksgiving.

Written and partly performed by Martin O'Donell and Michael Salvatori, the track also features some guitar shredding courtesy of real-life guitar hero Steve Vai. Vai got his start playing with Frank Zappa, has since played with Whitesnake, participated in the guitar-centric G3 tour, and showcased his skills in the 1986 film Crossroads, where he was the devil's surrogate axe-man in a guitar duel for the soul of Ralph Macchio's character.

This is the second time Activision has produced free Guitar Hero III track downloads. The first such offering allowed players to play the game's three boss battles all the way through as standard songs apart from the game's career mode.