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.

[2] A voucher for an exclusive 5-song demo of Rock Band Unplugged that is compatible with downloadable content was included with the PSP Go.

During the Quick Play and Tour modes, gameplay is similar to Harmonix' previous games Frequency and Amplitude: The player presses combinations of buttons on the PSP to match notes in time with the rhythm of the currently-selected instrument.

[4] Successfully completing multiple phrases in a row builds a score multiplier, as well as allowing the song to play in its entirety.

Tracks will not play automatically, causing the Crowd Meter for unselected instruments to continually drop in Band Survival Mode.

[2][6] Ten songs were made available for download on the day of the game's release,[7] and two new songs were released each week until November 19, 2009, when further DLC development was cancelled; Harmonix, while stating that Unplugged has "run through [its] planned state", has not ruled out future downloadable content but are presently focused on other Rock Band projects.

On March 10, 2010, Rock Band Unplugged Lite was released on the PlayStation Network, which is a downloadable version of the game.

[22] Reviewers praised the use of sound, particularly the slight volume emphasis given to the current instrument that is being played, though recommended the use of headphones to overcome the poor speaker quality of the PSP unit.

[18] IGN's Greg Miller lamented that unlike the social nature of Rock Band on consoles, the lack of such interaction cooperative or competitively with a second player leaves little reason to come back to the game or purchase additional content.

[21] The cost of additional downloadable content, even in consideration of it being more of the same that already exists in the Rock Band series, remains the same, from $0.99 to $1.99 a song.