quote Wikipedia

Confirmed Information:

Guitar Hero II is scheduled for a November 7, 2006 release date and will feature at least 55 songs, the majority of which will be licensed tracks covered in-studio. Guitar Hero Gibson SG controllers have been confirmed to be compatible with Guitar Hero II, and the sequel will feature the debut of three button chords, requiring players to press three of the buttons on the controller at once to get the desired note.

Five new characters will join the roster of playable characters from the original game: these include a rockabilly player named Dax DeVille, a male Norwegian death metal guitarist similar to Axel Steel (Guitar Hero), a "rocker chick" similar to Judy Nails (Guitar Hero), what seems to be a Slash-like guitarist, and a seventies rocker guy similar to Clive Winston (Guitar Hero). In addition to the new characters, the new game will feature an overhaul of the graphics, venues, and motion-captured characters.

Marcus Henderson, guitarist for the band Drist and the lead guitarist on many of Guitar Hero's cover tracks for the original and sequel has claimed, "Heavy metal will get its due in Guitar Hero II."[3]

Guitar Hero developer John Tam has said that the game is a "lead guitar game first and foremost" in response to questions of whether or not one will be able to play bass or rhythm guitar in the single-player career mode.

Guitar Hero producer Elena Seigman has confirmed a few changes to the way notes are played. Pull-offs will no longer require the lower note to be held and the window for succesfully hammering-on has been tweaked. There will no longer be chords that require holding the green and orange buttons at the same time.

Additions to the game modes include:

* Practice mode. The player will be able to choose from predetermined sections of a song such as "Verse 1", "Bridge", "Chorus" or "Solo 1", and will also have the option of moving the notes at four different speed settings.[4][5]
* An expanded multiplayer section gives two players the chance to engage in many different modes of play such as:
o Co-op mode, where each player is given a section of the song to play; one player will be playing lead while the other will be playing rhythm or bass guitar, depending on the song. In co-op, the song can be failed, unlike the original game's multiplayer. Both players share star power, the rock meter, the multiplier and a total score. In order to activate star power, both players will need to raise their guitar necks in a near simultaneous motion. Co-op mode will not have a practice feature.
o Traditional mode, similar to the original in which both players trade off sections of songs to play.
o Pro Faceoff mode, similar to the original again, but now both players are playing the full song note for note.
o Survival mode, the features of which have not been confirmed yet but have been rumored to either involve playing as long as possible without missing a note or failing a song.
o Handicapped versus mode, allowing one player to drop to a lower difficulty in order to level the playing field, the actual play likely being similar to co-op mode.

quote Guitar Hero Official Site Forum

Confirmed Information:

NEW-Multiplayer will include a pro faceoff mode which will allow both players to play the exact same notes.

NEW-The game will feature in-game endorsements and real world venues.

NEW-The game will feature at least two new characters, a rockabilly character named Dax Deville and an un-named norwegian black metal.

NEW-hammer-ons an pull offs have been tweaked. You will no longer have to hold down the lower frets to pull them off and the window of success for hammer-ons has been tweaked.

NEW- The game will feature a new venue lighting system that sync up the music being played to the lighting.

-At least 55 songs total, 40 licensed songs, 15 indie/in-house songs

-3-button chords, meaning, holding down green+red+yellow, yellow+blue+orange, etc.

-Increased Difficulty

-Practice Mode will feature pre-set sections of songs where you can play, loop and even slow down the track to get used to the fingering.

-Guitar Hero I SG Controllers will be compatible with Guitar Hero II.

-A new multiplayer co-op mode allowing players to collaborate in order to beat songs, with each guitarist playing a separate guitar track. Available guitar tracks include lead, rhythm or bass tracks, depending upon the song. Cooperative players will also share star power, both guitars must be raised for it to be activated. Also, both players will share one life bar.

-Co-op is not the only new Multiplayer Mode. Players can now play: Co-op (different instruments for each player), Traditional Versus (both players trading off notes), Full Versus (both players playing all notes), Survival (most likely play as long as you can without missing a single note, or trying to pass as many songs as possible on a single energy meter), and Handicapped Matches (one player has an advantage over the other).

-Career Mode has been changed, to quote an inside press release: "Players can now experience the feeling of going from an unsigned band to Rock-Stardom via artist endorsements."

-The Bass guitar will make deep clink and chunk sounds when you make a mistake, just like the regular guitars.

-Marcus Henderson has stated in an interview that "Heavy metal will get its due in Guitar Hero II".


Rumors and Pure Speculation

NEW-"Killing In The Name Of" By Rage Against The Machine. In the latest Official Playstation Magazine (Sept 06) on page 26 it talks about Raul Renteria, a QA tester who is very good at the game. "To prove this, Renteria played Rage Against the Machine's 'Killing in the Name' on Expert with his back to the screen, racking up a near perfect score."
Link: http://forum.guitarherogame.com/Default.aspx?g=posts&t=4142&p=4

-"The New Black" By Every Time I Die. During their performance at the Vans Warped tour Keith Buckley, vocalist for the band, stated that their song "The New Black" would be featured in Guitar Hero 2.
Link: http://ps2.ign.com/articles/716/716477p1.html

-A song by DragonForce. When a band is documented playing Guitar Hero, speculation is bound to arise. Much like Danny Carey from Tool, and The Darkness, the two guitarists for power metal band "Dragonforce" were spotted playing Guitar Hero. DragonForce is a much requested band for Guitar Hero II, and one must conclude that the thought enters the band's minds that they could possibly appear in a sequel to the game that they are playing.
Link: http://video.ugo.com/player.aspx?articleID=18924

-A song by Tenacious D. "An official list of new music tracks hasn't been released yet, but PSM was told that we shouldn't be surprised to see some Tenacious D in the game."
Link: http://forum.guitarherogame.com/Default.aspx?g=posts&t=3527 Original info is in PSM.

-A song by Buckethead. Last year, Marcus Henderon said the following quote: "Without going too much into detail, i'll just say this. Buckethead is very much in our plans for GH2. How? who knows... Where? you'll find out... Why? Cuz he's Buckethead. period."
Link: http://forum.guitarherogame.com/Default.aspx?g=posts&t=546

-A song by Descendents. Marcus Henderson, who recorded songs in both games is also on the song choice committee for Guitar Hero II, he stated in an interview that he has "been in dialogue with Bill Stevenson, their legendary drummer, and I totally want to get them in the game". So we will see what comes out of that. Descendants are an influential early Punk Rock band.
Link: http://ps2.gamespy.com/playstation-2/guitar-hero-2/703854p1.html

-A song by Tool - MTV.com stated that Tool are "in talks to be featured in the forthcoming "Guitar Hero 2" video game".
Link: http://www.mtv.com/news/articles/1531583/20060511/tool.jhtml
EDIT: I have confirmed with RedOctane that Tool and RedOctane have spoken regarding having a song in the game. Nothing has been decided as of 5/18/06.

-"Wasted Years" by Iron Maiden
Marcus Henderson said the following line, though, it's worded largely rhetorical: "I LOVE MAIDEN!!!!!!!!!!!!! One of my favorite bands ever. How would you guys feel about Wasted Years in GH2?"
Link: http://forum.guitarherogame.com/Default.aspx?g=posts&t=603

-"For Those About To Rock" by AC/DC - RedOctane issued a press release for Guitar Hero II, and the title of the release is "For Those About to Rock With Guitar Hero II, We Salute You! RedOctane Announces Fall US Tour Date" Of course, the first sentence of the title are lyrics and the name of a song by AC/DC. The song has not been confirmed, but it seems odd to make such a possible hint if it was unfounded.
Link: http://www.redoctanegames.com/2_press/viewer.asp?screen=2006-04-17_gh2announce.html

-White, Green, Yellow, and Sexy Pink SG controllers were all seen at E3 2006. However, these could be custom made controllers that will never see the light of day.