Since the release of the first Rock Band, Harmonix has revealed that there have been over 28 million downloads of songs released on the PlayStation Network and Xbox Live Marketplace.
Since its debut on these two platforms, 345 songs have been made available for download by gamers by some 239 artists. Since its first downloadable content was released, Harmonix has released content on a weekly basis for 55 weeks straight.
Source
Since its debut on these two platforms, 345 songs have been made available for download by gamers by some 239 artists. Since its first downloadable content was released, Harmonix has released content on a weekly basis for 55 weeks straight.
Source