It wasn't hard for Black Sabbath guitarist Tony Iommi to get Henry Rollins to appear on his all-star solo debut, Iommi.

All he had to do was play Rollins the riff for "Laughing Man (In the Devil Mask)."

"I said, 'Whoa, that's Iommi,' " said Rollins, who jumped at the chance to write lyrics and sing on the track. "To have your voice synched up with that sound for three or four minutes in your life, to me, that is a stone-cold honor."

That kind of reaction was shared by other guests on the disc who had grown up with Iommi's thick, crunching guitar tone in such Sabbath classics as "Iron Man," "Paranoid" (RealAudio excerpt) and "War Pigs."

Smashing Pumpkins head Billy Corgan, Foo Fighters frontman Dave Grohl and Pantera leader Phil Anselmo were among the disc's contributors, along with such veterans as Billy Idol, the Cult's Ian Astbury and Sabbath foil Ozzy Osbourne.

"They did all the lyrics and melodies they were singing," Iommi said of his guests. "I wouldn't ask somebody to come in and join me on a track and tell them what to do. The whole purpose of it was the amalgamation of it all, to see what happens."

Album Long-Planned But Spontaneous

What happened was a collaborative effort, released Oct. 17, that might be viewed as a hard-rock cousin to Santana's Supernatural in its mix of youth and experience.

"A few people have said that — that it's a heavy version of the Santana thing — but I've had the idea for a few years," said Iommi, who was delayed by a reunion tour of the original Sabbath. "It's just more or less that he beat me to it.

"I wanted a selection from old to new [singers], which I've got. The only one I couldn't get was Tom Jones. I wanted to get him on, but he was too busy at the time doing his own project.

"You never know what you're letting yourself in for when you're getting involved with other people. So it was actually great to get into the studio together and really click — and we all did. It's amazing. I was very impressed with the way each one of them worked, just the different characters and the way they took the songs on."

At times, the process was spontaneous, as when Corgan arrived at the studio with then-Pumpkins drummer Kenny Aronoff and picked up a bass to carve "Black Oblivion" (RealAudio excerpt) from a jam.

"In the morning, we came up with a riff, and in the afternoon, we were putting it to tape," Iommi said. "Billy was writing the lyrics while I'm doing some overdubs."

Nonetheless, there's surprising continuity to the tracks, which shift from the emotionally volcanic "Meat" (RealAudio excerpt), with singer Skin of Skunk Anansie, to the melodic majesty of Grohl's "Goodbye Lament" (RealAudio excerpt) to more brooding takes from Type O Negative's Peter Steele and Serj Tankian from System of a Down.

Sound Crafted Before Sabbath

In the Osbourne track, "Who's Fooling Who," Iommi found some familiar chemistry. "I didn't actually intend to have Ozzy on the record. I'm really glad he did it," he said. "We were sitting down together one day, and Ozzy said, 'Aren't you going to have me on the album?' I said, 'Ah, sure.' "

Sabbath drummer Bill Ward was also at that table, and wanted in. "I more or less had a sound before we actually got together as Black Sabbath," Iommi said. "I was in a band with Bill Ward and we played a lot of blues and stuff, loads of guitar solos, and I developed a sound from that.

"When we first came out with Black Sabbath, nobody was doing anything like that. It was the whole mood of it, just because it was heavy and loud and doomy. It just hit a spot with everybody."

Rollins included. "I'm such a fan, I had him sign my lyric sheet," the tattoo-clad vocalist said. "He means a lot, and his band and his music have meant a lot to people for decades. Black Sabbath is one of the most universally spoken languages in music."

In addition to the singers who brought their own lexicon to Iommi's solo project, guests included Pearl Jam drummer Matt Cameron (who was reunited with ex-Soundgarden bandmate, bassist Ben Shepherd) and Queen guitarist Brian May.

"There's no way you could have done this in the '70s," said Iommi, who remembers catching flak from his Sabbath mates for appearing on a solo record by Procol Harum's Bobby Harrison that even tapped horns from Tower of Power. "Everybody was into their own band, and if you ventured out of that band, you were a traitor."

Things are different now — apart from the timeless sound of Iommi's Gibson SG. "The original guitar I kept under lock and key, and it will remain there unless somebody offers me $100,000 for it, and then it will go away," Iommi said, before reconsidering. "No, I'll keep that. That's my history there."