Although players may have toured the world many times over in the console editions of Rock Band, the series can finally take its act on the road with Rock Band: Unplugged, the first for a portable system. The game is played with the normal PSP buttons instead of frets on a guitar-shaped controller, not unlike the play in developer Harmonix's Guitar Hero pre-cursors for PS2, Frequency and Amplitude. As icons scroll outward down the screen, players tap buttons in time with the music, in order to perform the part of the instrument they are playing. Players can switch between available instruments -- lead, bass, drums, and vocals -- by shifting to the left or right. The game's song list includes more than 40 master recordings, including 9 tracks that launch as system exclusives for a limited time before being made available to other system editions of Rock Band.