For Geezer Butler, who was expecting to be joined by original drummer Bill Ward in the Black Sabbath rhythm section for the band's reunion, the arrival of Brad Wilk must have come as a bit of a shock. Luckily, it seems the drummer from Rage Against the Machine fit in just fine.

"I was really surprised," the bassist tells Guitar World in its forthcoming April edition. "He had that Bill Ward kind of jazzy swing feel, rather than heavy metal bashing." Wilk was suggested for the job by album producer Rick Rubin, who produced Rage's 2000 studio album 'Renegades.'

The group spent a year writing for the '13' project, Black Sabbath's first studio effort with Ozzy Osbourne at the helm since 1978. But when it came time to hammer out a contract prior to recording, Ward and the band couldn't come to terms.

Producer Rubin suggested Wilk, and Sabbath has now completed 16 songs. That total will be cut down to nine or 10 for the album's final song list. Guitar World reports that three of the cuts -- 'End of the Beginning,' 'God is Dead' and the appropriately titled 'Epic' -- clock in at more than seven minutes.

The magazine talked to Butler and Osbourne at the erstwhile Black Sabbath frontman's home in California. Guitarist Tony Iommi missed the interview so that he could undergo a final round of treatment back in the UK for lymphoma. '13' is set for release in June.