Los Angeles ? Dave Grohl, who describes himself as a 36-year-old teenager, may 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 Springfield, Va., native is still a rocker with bite, humor and chutzpah, but also a singer and songwriter ready to showcase his softer side and take risks.

“We’ve been making those four-and-a-half 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 told The Associated Press. “The acoustic album was our way out. That was the emergency exit. The rock disc sort of 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, in 1990, because it made “perfect sense” though it was written 15 years ago.

The Foo Fighters, from left, Nate Mendel, Taylor Hawkins, Dave Grohl and Chris Shiflett are photographed before their concert in Duluth, Ga. On In

Then 21, Grohl had just moved to Olympia, Wash., 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 6 a.m. 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 best-selling 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 band mates.

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, Va., where the band recorded 1999’s “There is Nothing Left to Lose” and 2002’s “One By One.”

While the guys considered guest rock stars such as Led Zeppelin bassist John Paul Jones and Queens of the Stone Age guitarist Josh Homme 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,” said Shiflett. “I thought, ‘Why would we do that?’ You think it’s going to be a bad idea, but it just works.”

On the threshold of the Foo Fighters’ U.S. tour with Weezer, which started Thursday in Atlanta, Grohl said 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.