While the music industry struggles to sell CDs, Microsoft revealed yesterday that gamers purchase around 3.8 million Guitar Hero and Rock Band downloads per month via their XBox Live network. Between all versions of the two titles, the pair have sold around 45 million song downloads at a typical price of $1.99 each. Since the 360-exclusive release of Rock Band 2 in mid-September, the game has thus far sold 363,000 copies. RB2 was finally released for PlayStation 3 this past weekend, while the Wii release arrives in December. Meanwhile, Guitar Hero: World Tour, complete with drums and microphone add-ons to compete with Rock Band, hits stores this Sunday.