A full version of the game was leaked on a number of torrent sites on May 17, 2009. It includes an option for downloadable music.Destructoid: Rock Band Unplugged leaks (May 17, 2009)

1. Publisher: Electronic Arts, MTV Games, Harmonix
2. Developer: Backbone Entertainment
3. Platform: PSP
4. Genre: Rhythm/Music
5. Modes: Single-player
6. ESRB Rating: T (Teen)
7. Release Date: June 19, 2009Joystiq: Rock Band Unplugged detailed, priced and dated (April 8, 2009)

Other outlets have reported that the game will not make use of any external peripherals, instead containing gameplay similar to Harmonix' previous PS2 releases, Frequency and Amplitude. In those games, the music was divided into separate tracks, and the player pressed buttons on the controller in time with the beat to capture "phrases" before moving on to the next track.Primotech: EA Publishing Rock Band Unplugged for the PSP

The game is reported to be in development at Backbone Entertainment, a studio that's developed a number of games for the PSP, including the Death, Jr. series of games, NBA Ballers: Rebound, and The Sega Genesis Collection among others. Some of Backbone's other releases include Super Street Fighter II Turbo HD Remix and Super Puzzle Fighter II Turbo HD Remix for Xbox 360 and PS3Developer Site: Backbone Entertainment