Fans of the music-based games "Guitar Hero III: Legends of Rock" and "Rock Band" have purchased and downloaded more than 7 million additional songs - beyond the ones included on the games -- since they were released late last year.

"Guitar Hero III" was released Oct. 28 and began offering new downloadable songs the following week. The game's publisher Activision tells Billboard more than 5 million songs have been downloaded since, in three-song bundles, consisting of both new songs developed for the game as well as songs that appeared in previous versions of the game.

MTV, responsible for "Rock Band," reports that 2.5 million songs have been downloaded, both as singles and three-song bundles, since it began offering them Nov. 20.

For a full report on the numbers, and their impact on the music industry, look for the story in the new issue of Billboard.