D ave Grohl, who describes himself as a 36-year-old teenager, may finally be growing up.

True, the Foo Fighters frontman espouses whiskey as a cure-all for colds, has wrapped himself in aluminum foil on national television, and holds a soft spot in his heart for death metal. But on In Your Honor, the Foo Fighters' surprising new double disc and fifth album, Grohl dramatically expands his band's sound, splitting the album's 20 songs between characteristically explosive electric tunes, and quiet, acoustic numbers.

Ten years after the Foo Fighters picked up where Nirvana left off, the Virginia native is still a rocker with bite, humor and chutzpah, but also a singer-songwriter ready to showcase his softer side and take risks.

"We've been making those 4-minute-long, catchy rock songs for 10 years, and I thought, `If we ever want to break out of that mold, we're going to have to do something a little drastic or a little different,"' Grohl says.

"The acoustic album was our way out. That was the emergency exit. The rock disc represents the last 10 years of the band, and the acoustic side represents 10 years to come."

Grohl decided to include Friend of a Friend, the first acoustic song he wrote, because it made "perfect sense" although it was written 15 years ago.

Then 21, Grohl had just moved to Olympia, Washington, and lived with late singer Kurt Cobain in a small dump of an apartment as Nirvana's new drummer. They would go to sleep at 5 or 6am and wake up at 5 or 6 at night, he said.

"We saw no sunlight. I was lonely and depressed. It was winter. There was an acoustic guitar in the room and I started writing this song about Kurt and [bassist] Kris Novoselic, these strangers I had just met."

From the heavy thrust of bestselling single Best of You to the slow bossa nova of Virginia Moon, in which Grohl smoothly duets with Norah Jones, In Your Honor is also a testament to the musical capabilities of Grohl's three current bandmates.

After spending time on various side projects, bassist Nate Mendel, drummer Taylor Hawkins and guitarist Chris Shiflett hunkered down to record the ambitious album at Grohl's new home studio in Los Angeles, far from Alexandria, Virginia, where the band recorded 1999's There is Nothing Left to Lose and 2002's One By One.

While the guys considered guest stars such as Led Zeppelin bassist John Paul Jones and Queens of the Stone Age guitarist Josh Homme as natural contributors, mainstream jazz-pop chanteuse Jones proved at first to be a less popular pick.

"I'll be the first to admit I wasn't into the idea of her," says Shiflett. "I thought: `Why would we do that?' You think it's going to be a bad idea, but it just works."

Grohl, who dropped out of high school, worked in furniture stores as a teenager and was never formally trained as a musician, says he'll work with anyone he thinks is talented.

"If there's one thing that's always bothered me, and I think this is from growing up in Virginia, it's the `cool factor' that comes along with playing music," he says. "I like Creed songs. I like Leonard Cohen. I did sheets of acid and listened to satanic heavy metal as a kid."

On the threshold of the Foo Fighters' US tour with Weezer, Grohl says the band will concentrate on performing their album's thunderous "rawk" disc. However, a second tour of acoustic songs at smaller venues is planned for next year. For now, political as well as musical rage has figured into the mix.

The title song In Your Honor - with its pounding lyrics "Hear me screaming/Breaking in the muted sky" - was inspired by Grohl's experiences in 2004 on the campaign trail with presidential hopeful John Kerry.

"I was inspired by the feeling of devotion to him. People were so passionate and moved. But the songs are general ideas, not specific dedications," Grohl says.

Shiflett's response to getting involved in the Kerry campaign led him to invite progressive groups Democracy for America and Campus Progress to join the Foo Fighters' new tour.

"In the aftermath of the election, I was pretty disappointed and wanted to do something more concrete," he says, adding he hopes the grass-roots groups will motivate Foo Fighters fans of all stripes to become active in local politics.

As for the future, anything is possible for the band whose long career bassist Mendel once called "accidental."

Grohl, married with a stable home life, says he most looks up to Neil Young, a relentless musician with "a beautiful family, who makes albums when he feels like it and is just as bad- ass as he was 30 years ago."

Eventually, Grohl said he would like to score movies in the vein of one of his other mentors, former Police drummer Stewart Copeland.

"This seems like the retirement plan. When your knees give out, and hangovers last too long, you gotta get off the road," he says.

"Do I think the Foo Fighters will last for another 15 or 20 years? No. Do I think I'll be making music with those three guys for the rest of my life? Yes. You just have to decide when it's time to back out."

ASSOCIATED PRESS