Rock Band Blitz is a rhythm game in the Rock Band series, available as a downloadable game for Xbox Live Arcade and PlayStation Network. Unlike previous iterations of Rock Band, Blitz does not use special instrument controllers, instead allowing the player to use a regular console controller to match notes in a song, using gameplay mechanics similar to Harmonix' previous titles of Frequency, Amplitude, and Rock Band Unplugged. In addition to 25 songs that will ship with the game, the title is capable of using any songs the player has downloaded or exported for Rock Band 3.
Source: Wikipedia, "Rock Band Blitz", available under the CC-BY-SA License.