The June issue of Game Informer magazine has some tasty little tidbits about Guitar Hero IV. Namely multiple instruments and custom song creation.
The custom song creation feature even allows you to upload your song so others can download it. Looks to be a pretty sweet promo tool for young bands, although it seems you won't be able to customize the vocals. So, maybe its just a sweet promo tool for ProgRock bands. NICE.
Neversoft has also assured us that all the tracks will be master recordings and they have some bands involvement already confirmed. I'm talking Van Halen, Eagles, Linkin Park (who need to learn how to spell,) and Sublime.
shacknews.com: Guitar Hero 4 Includes Song Creation and Sharing...
'Guitar Hero 4' News