Tom Morello wants as many "what the f***" factors in his music as possible.

The Rage Against The Machine guitarist - who released his second solo album 'The Atlas Underground Fire' last month - has opened up about his need for innovation when it comes to how his instrument sounds on different songs.

He told Guitar World magazine: "That's been the common thread through everything, whether it's an 'Atlas Underground' record or an Audioslave record. I need to feel a jam move air, but I also want it to challenge me.

"[Living Colour founder] Vernon Reid called it the 'What the f***' factor, you know? Like, when you put on a record and you hear what must be a guitar but can't possibly be a guitar, you're like, 'What the f***?'

"I remember thinking about that over and over again as a young person, and as a young guitar player. Every record I make, I try have as many 'What the f***?' factors as possible."

This mentality manages to complement his "cornerstone" which is "unapologetically and uncompromisingly big rock 'n' roll", while he always strives for some level of innovation.

He explained "I mean, the first cornerstone of my playing is unapologetically and uncompromisingly big rock 'n' roll, and I will never budge an inch on that.

"That's what I get off on the most, going back to the first AC/DC and KISS and Led Zeppelin posters on my wall. That just feels right and feels like home.

"At the same time, the other cornerstone of my playing has been to just disregard anything that has to do with tradition, whether it's melody or tone or sound, or even what part of the guitar to look at as a sound-maker."