Black Sabbath riff meister Tony Iommi took some time to discuss an extensive riff collection he compiled over the years, revealing he rarely returns to material he once put aside."I have got a closet full of riffs, but I very rarely go back to them, to be honest," he told SF Weekly. "I always think, 'Well, I'll put this away, and I'll put that down,' and when it comes time to do something, I always seem to come up with something new."When asked on what makes a riff good enough to earn it a spot on the record, Iommi replied: "I have to feel it in myself; it comes from within. You do a riff and you think, 'Oh yeah, I really like this.' I'll go back to [it] and listen to it again and go, 'Yeah, I like this.'"I mean I've done thousands and thousands of them. I can walk into the studio and play for a couple of days and just come up with no end of riffs. I might not ever use them."Despite expressing uncertainty over ever recording a new Sabbath album, the axeman recently pointed out that the feeling onstage among the ranks of metal pioneers is better now than 40 years ago.The band's latest studio effort, "13," hit the shelves on June 10 through Vertigo Records, topping both the UK Albums Chart and the Billboard 200 chart with 155,000 units shipped in the US within the first week.