Slayer's Kerry King writes new riffs every time he picks up a guitar.

The 'Reign in Blood' musician has been playing for over 30 years, and never finds it hard to write new tracks for his group.

He told Metal Hammer magazine: ''Anytime I pick up a guitar, a riff comes out of it.

''You have to not get cheesy or caught up in yourself. I'm still looking for the perfect riff. We've got a lot you could say are perfect, but it's like the Holy Grail, you just keep looking for that f***er.''

Slayer also includes bass player and singer Tom Araya, drummer Dave Lombardo and guitarist Jeff Hanneman, although Gary Holt has stood in for the latter since 2011, after he contracted flesh eating disease necrotizing fasciitis and was left unable to play.

The band try to recreate their songs as closely as possible to their records when they play live, but Kerry admits he sometimes forgets his older parts.

He explained: ''Sometimes we mix up our set and play songs we haven't played in years and it's like, 'F**k.' Gary never played on the album, and he's asking me how to play riffs I haven't thought of for years.I'm like, 'I dunno, go ask Tom! I can't even help you!'''