Foo Fighters released their fifth album, the two-disc set "In Your Honor," in June. Disc One features hard-edged rockers, while Disc Two largely houses acoustic tracks.

"Everyone in the band has so much to offer," Grohl said in the band's record company biography. "But we'd sort of remained in this one 'thing' for so long that I felt it was time to break out, to branch out, that maybe we should make the acoustic record--but then I started thinking about how I didn't want to show up to the Reading Festival with a harpsichord, or whatever. This band just has to make some rock music so I thought, OK, why don't we do this? Why don't we make a double album?"

Splitting the difference gave the band the freedom to eliminate the middle ground, Grohl said. "We can make the acoustic record far more delicate and beautiful and atmospheric than anything we've ever done, and we can make the rock record far more brutal and aggressive and powerful than anything from our past."

During a June appearance on "The Howard Stern Show," Grohl said that the Foo Fighters planned to embark on a fall tour with fellow modern rockers Weezer. Details of that outing, which could launch in September, haven't been announced.