Within the last year, Ohio duo The Black Keys [ tickets ] worked with Gnarls Barkley's Danger Mouse on its own album, as well as iconic rock star Ike Turner on his project. Both collaborations allowed the band--whose feet are firmly planted in blues-rock--to expand its sound.

"I think that Pat [Carney, drummer] and I knew we wanted to use lots of instrumentation on this new record," said guitarist/vocalist Dan Auerbach of "Attack & Release." "We brought all the instruments from home, all the weird s--- that we had.

"We always use different instruments on records, but never to this extent. We've always experimented in the studio. Pat and I listen to all kinds of music. It didn't feel like we were forcing ourselves to do anything. It seemed like a natural progression, obviously."

On The Black Keys [ tickets ]' first record, 2002's "The Big Come Up," the album was stripped down, though the duo dabbled in synthesizer, Auerbach said. By the third album, "Rubber Factory," "we had all kinds of s--t."

"The natural progression was sped up a little bit with Danger Mouse being there to lend support," Auerbach said.

The duo further credited Danger Mouse (born Brian Burton) for making the "Attack & Release" sessions "productive."

"It was sweet working with Danger Mouse," Auerbach said. "He's a cool guy. Above everything else, we got along as friends. It was really easy to work with him when we got into the studio. Everybody had their equal say and could throw out ideas. It's just really productive. There was no ego involved with anyone. It just made it really easy to keep things rolling. Danger Mouse was just another guy to bounce ideas off of. If we'd get stuck in a rut, he could keep us moving forward, keep us focused. When we were just doing fine on our own, he would just stand back and let us work. It was perfect."

The album features guest appearances from guitarist Marc Ribot and multi-instrumentalist Ralph Carney (Patrick Carney's uncle), both of whom have spent time in Tom Waits' band. The album also features vocal contributions on the closing track from 18-year-old bluegrass singer Jessica Lea Mayfield.

As for the Turner project, Auerbach said he and Danger Mouse wished they could have finished the project before Turner's drug-related death last December.

"We were going to finish our record and then get back to it," Auerbach said. "A month or two after our record was done, we found out he passed away. It kind of sucked. [The material we were working on with him] was really cool. What we were getting accomplished was pretty awesome. It really was."