Green Day: Rock Band allows players to perform simulated rock music by providing up to four players with the ability to play three different controllers modeled after music instruments: a guitar controller for lead guitar and bass guitar gameplay, a drum controller and a microphone for vocals. Players simulate the performance of rock music by using their controllers to play scrolling on-screen notes. For lead and bass guitar, this is accomplished by holding down colored buttons mimicking guitar frets and pushing the controller's strum bar. For drums, this requires striking the matching colored drumhead, or stepping on the pedal to simulate playing bass drum notes. When singing vocals, the player must sing in relative pitch to the original vocals. A pitch indicator displays the singer's accuracy relative to the original pitch. The game supports harmonies as introduced in The Beatles: Rock Band, allowing multiple singers to perform the vocal portion.[2] Harmonies will be added to the six songs already available as downloadable content for the game when played in Green Day: Rock Band.[3]
As in previous Rock Band games, successfully hitting the proper notes in sequence earns points for each player and boosts their "performance meter". If a player fails to match the notes, their performance meter drops. If the meter empties, that player is forced to drop out of play, temporarily silencing that instrument and causing the band's overall performance to drop. Any player to drop out can be "saved" if another player activates "Overdrive", which is collected by successfully completing specially-marked phrases, and for guitar and bass players, using the controller's whammy bar to alter the pitch of marked sustained notes. Overdrive can also be used to temporarily increase the number of points the band earns. Activating Overdrive is specific to each "instrument". For guitar, the controller must be temporarily shifted to an upright position; for drums, a specific drumhead must be hit at the end of a drum fill when prompted; and for vocals, a noise must be registered by the microphone when prompted.[3] The game does not feature any "Big Rock Endings", which allowed players to improvise at the end of a song for additional scoring as in the other Rock Band games, nor includes any clapping or tambourine sections for the vocalist player, due to lack of places in Green Day's songs to include the features.[3] Immediately before playing a song, players must choose their difficulty level; ranging from "Easy" to "Expert". A "No Fail" mode has been carried over from Rock Band 2 and is accessible from the difficulty menu. Players are also able to identify their handedness for guitar, bass, or drums before the start or during a song via the game's "pause" menu. Upon completing a song, the players are given a star rating, from 1 to 5 stars, or 5 gold stars for very high scores if all band members are playing on Expert.
Green Day: Rock Band features a Career mode, similar to The Beatles: Rock Band. However, it allows the player to immediately select any of the available songs and records to play from the start instead of stepping through specific sets.[4] The Career mode has a "meta-game" through various challenges that subsequently unlock additional rewards (photographs or videos contained on disc), such as by completing every song in a specific set with a 4-star rating or higher.[3] Some challenges require the players' band to earn enough "cred" to unlock them; these additional challenges three or four song challenges built around certain themes.[3] A Quick play mode allows players to select one of more of the songs available to the game to play outside of Career mode.[5] A drum trainer mode is available to help players become accustomed to the instrument controller. The trainer includes a set of stock rhythms that are generic for most songs, and a set of "Tre's Greatest Hits" with drum patterns and solos taken from Tré Cool's performances, including one "ferocious" solo that runs across two different lessons.[5]
