At the main menu, select "Options", "Cheats", "Enter New Cheat", then enter one of the following codes to unlock the corresponding cheat option. If you entered the code correctly, a message will appear.

Unlock All Characters - Press Blue(2), Green(2), Red, Green, Red, Yellow.

Auto Kick - Press Yellow, Green, Red, Blue(4), Red. This mode automatically plays the bass pedal for the drummer. Alternately, hit 200 non-cymbal notes on the "Mirror People" song at the Angel's Crypt venue as a drummer. Note: Fills do not count towards the total.
Always Slide

Press Green(2), Red(2), Yellow, Blue, Yellow, Blue. This mode turns all guitar notes (not chords) into touch pad sliding notes connected by purple lines. Alternately, hit 230 tap notes on the "Du Hast" song at the Neon Oasis venue as a guitarist.
All HOPOs

Press Green(2), Blue, Green(3), Yellow, Green. This mode changes almost all notes into hammer-on/pull-off notes. Alternately, whammy sustain notes on the "Hurts So Good" song for at least 25 seconds total at the Club Boson venue as a guitarist.
Focus Mode

Press Yellow, Green, Red, Green, Yellow, Blue, Green(2). This mode blacks out the background. Alternately, hit 265 tom-tom notes on the "Brianstorm" song at the Golden Gate venue as a drummer to unlock Focus mode under the "Extras" menu.
Performance Mode

Press Yellow(2), Blue, Red, Blue, Green, Red(2). This mode removes the track and HUD. Alternately, get a band multiplier with two players for 42 seconds on the "Bleed American" song at The Aqueduct venue to unlock Performance mode under the "Extras" menu.
HUD Free Mode

Press Green, Red, Green(2), Yellow, Green(3). This mode removes the rock meter, star power gauge, and score display. Alternately, get "Excellent" on 75 consecutive phrases on the "Bring The Noise 20XX" song at the Neon Oasis venue as a vocalist to unlock HUD Free mode under "Extras" menu.

Invisible Characters - Press Green, Red, Yellow(3), Blue(2), Green.

Air Instruments - Press Red(2), Blue, Yellow, Green(3), Yellow. This mode makes all instruments almost invisible; however, the guitar strings can still be seen. Alternately, strum at least 340 chords on the "Sultans Of Swing" song at the O'Connel's Corner venue as a guitarist.

Contest Winner 1 - Press Green(2), Red(2), Yellow, Red, Yellow, Blue.

Absolutely Nothing - Press Red(2), Green(2), Blue(2), Yellow(2).

Wormhole Quickplay mode venue - Get a 4X multiplier for 50 seconds on the "Play That Funky Music" song at the Sideshow venue as a guitarist to unlock the Wormhole Quickplay mode venue. Note: This venue is required for The Grand Tour.

Bonus characters - Successfully complete the indicated task in Career mode to unlock the corresponding character:

Carlos Santana: Successfully complete the "No One To Depend On (Live)" song.
Johnny Cash: Successfully complete the "Ring Of Fire" song.
Kurt Cobain: Successfully complete the "Smells Like Teen Spirit" song.
Matt Bellamy: Successfully complete the "Plug In Baby" song.
Shadow: Get a 600 note streak on the "Lust For Life (Live)" song.
Shirley Manson: Successfully complete the "I'm Only Happy When It Rains" song.
Skeleton: Successfully complete the Platinum or Diamond drum challenge for the "Brianstorm" song.
The Golden God: Successfully complete the Platinum or Diamond challenge for The God Of Rock's Final Challenge.

Alternate costumes - Successfully complete the indicated song challenge to unlock the corresponding costume for the pre-made character:

Axel Steel's Battle Scar costume: "Medicate" challenge
Axel Steel's Hog Wild costume: "Send A Little Love Token" challenge
Axel Steel's Shoulder Blades costume: "Sympathy For The Devil" challenge

Casey Lynch's Flying Trapeze costume: "Superstition" challenge
Casey Lynch's Monochrome Maiden costume: "So Lonely" challenge
Casey Lynch's Sharpshooter costume: "In My Place" challenge
Clive Winston's Deer Scout costume: "Sneak Out" challenge
Clive Winston's Persuader costume: "Blue Orchid" challenge
Clive Winston's Sugar Daddy costume: "Shout It Out Loud" challenge

Eddie Knox's Casual Wednesday costume: "Gamma Ray" challenge
Eddie Knox's Crusier costume: "Make It Wit Chu" challenge
Eddie Knox's Suede Spade costume: "Six Days A Week" challenge

Izzy Sparks' Impresario costume: "Feel Good Inc." challenge
Izzy Sparks' Sideshow costume: "Scatterbrain" challenge
Izzy Sparks' Stiki costume: "Jailbreak" challenge

Johnny Napalm's 1976 costume: "Judith" challenge
Johnny Napalm's Generation Zzyzx costume: "Looks That Kill" challenge
Johnny Napalm's Suburban Snot costume: "Fame" challenge
Judy Nails' Big Knee Pin costume: "Gratitude" challenge
Judy Nails' Mall Chic costume: "Runnin' Down A Dream" challenge
Judy Nails' The Riot Starts Here costume: "You Give Love A Bad Name" challenge

Lars Umlaut's Grendel costume: "All Along The Watchtower" challenge
Lars Umlaut's Soldier of Farce costume: "In The Meantime" challenge
Lars Umlaut's Valhalla costume: "We're An American Band" challenge

Pandora's Gretel costume: "Steady, As She Goes" challenge
Pandora's State of Fluxus costume: "Back Round" challenge
Pandora's Strapped costume: "L.A." challenge