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.