Rock Band Unplugged is an expansion of the Rock Band series of music video games released for the PlayStation Portable. The game is developed by Backbone Entertainment in conjunction with Harmonix and is distributed by MTV Games and Electronic Arts. The game was released in North America and Europe on June 9, 2009. The core game is functionally similar to the note-matching gameplay of Harmonix's previous titles, Frequency and Amplitude, with the player responsible for playing all four instruments—lead and bass guitar, drums, and vocals—using the Portable's controls. Game modes are similar to Rock Band's, and the soundtrack includes a number of songs that have already been a part of the Rock Band series. Additional tracks will be a time-limited exclusive to Unplugged before they are released as downloadable content for the console games. The game supports the addition of new songs that can be purchased through the PlayStation Store. Rock Band Unplugged, in addition to being released separately, was also released as part of a "Limited Edition Entertainment Pack" that also includes a Rock Band Unplugged-branded PSP, a 4GB memory card, and a voucher to download the movie School of Rock. A voucher for an exclusive 5-song demo of "Rock Band Unplugged" that is compatible with downloadable content is included with the PSP Go.