Rock Band, the game released by MTV and Harmonix, is selling like hot cakes and its success is boosting the sales of the downloadable content.

MTV announced that since the launch of the game in November last year the gamers have purchased more than 2.5 million game levels based on songs.

"Our goal with Rock Band was to create an entirely new way for people to interact with the music they love," stated Van Toffler, president, MTVN Music Group/Logo/Films. "The incredible response to the downloadable content we've released to date motivates us even more to establish this platform as a way for people to discover new, up and coming artists through the game - in addition to delivering great game play experiences set to the music of mega-artists."

Rock Band is a party game that was released bundled with controllers shaped like guitar, drum set and microphone. The full package costs $170 and it seems the price doesn’t represent a problem among the music-themed video games fans.

The game includes 58 playable songs such as the Rolling Stones' Gimme Shelter and Metallica's Enter Sandman and it was released for Xbox 360, PS2 and PS3. More tunes can be downloaded over the PlayStation Network and Xbox Live for prices varying from 99 cents to $2.99.

A Metallica pack featuring three of the mega-platinum band’s most electrifying tracks—“Ride The Lightning,” “Blackened” and “And Justice For All”—is currently the game’s top-selling music download, followed by three-song packs from The Police, Queens of the Stone Age, David Bowie and a collection of Black Sabbath covers.

Top-performing singles are Foreigner’s early ‘80s hit, “Juke Box Hero,” followed by a cover of Creedence Clearwater Revival’s late ‘60s smash, “Fortunate Son,” Weezer’s mid-90s single “Buddy Holly” and a cover of The Knack’s blockbuster hit, “My Sharona.”

Also MTV intends to use the downloadable content as a way to promote new songs and albums. Rock Band represents the first act of MTV’s plan to spend more than $500 million on video games over the next two years as Viacom’s company expands beyond its TV base.