The emerging effort to use videogames as a channel for selling music is entering its next phase with the recent release of "Grand Theft Auto IV."
Phase I has proved a phenomenal success, with "Rock Band" and "Guitar Hero III" selling millions of songs through their respective platforms. But it has been a limited victory.
Both are music-based rhythm games that use master recordings and cover songs to let gamers "play" along to the tunes using special controllers shaped like musical instruments. Purchased songs can be used only as elements of the game itself. They can't be transferred to an MP3 player or stored in users' digital music libraries.