When Kurt Cobain died tragically and famously in 1994, there was talk that Nirvana's ferocious drummer, Dave Grohl, might go behind the kit with either classic-rock band Tom Petty and the Heartbreakers or grunge rivals Pearl Jam.

No one, not even Grohl, expected the drummer would step out front as a guitarist (his first instrument) a year later and lead the Foo Fighters through a series of platinum albums and even a Grammy nomination for Album of the Year.

Bassist Nate Mendel recognized the talent early on, which made it easier for him to make the transition from seminal emo band Sunny Day Real Estate to the Foo Fighters.

"We had some friends in common before I met him," Mendel says, "and before we started the band and I actually had heard some of the stuff he'd done and knew his backstory -- that he was a guitar player first and had always been writing songs -- so honestly, it wasn't that surprising to me. And then, before we actually became a band, I heard the first record that he recorded that was actually circulating Seattle as a demo tape, and I knew that this was a really talented songwriter. So it wasn't too much of a shock that he was able to grow and become the musician he is now."

The early Foo Fighters stuff revealed that, if nothing else, Grohl could scream with the best of them. And he still can. But over time, Grohl has shown more of his range, like a knack for acoustic ballads, and the Foos have evolved beyond being a raging quartet.

On the tour for the sixth album, "Echoes, Silence, Patience & Grace," which stops at the Petersen Center Saturday, the Foo Fighters are on the road with an expanded lineup.

"We're carrying this extended band now -- we've got a keyboard player, percussion, a third guitar and a violin player," Mendel says. "We went and did an acoustic tour with these same folks, and it was all quiet songs. This last record was written with those instruments in mind, and they were used in some of the rock songs and so we're going to play songs like 'The Pretender' as an eight-piece band and have it be this big, loud noise."

The risk, of course, is that it over-polishes the Foo Fighters and turns them into a different entity.

"Our solution to that has been, and I'm not sure it's the best one, is just to play longer. Rather than sacrificing what it is we've more traditionally done, because we have these other elements, we just make the show longer. We play well over two hours now, so it's like a standard Foo Fighters show with this other thing tacked on. It was just the natural flow of things."

The classic-rock influences and more elaborate instrumentation are prevalent now in songs like "Summer's End," "Statues" and "Stranger Things Have Happened."

"I think some of the songs Dave writes and his vocal style he has that timeless quality that the songs we grew up within the '70s have," Mendel says. "He's able to write a song that sounds fresh and yet something you're familiar with and have loved for a long time, all at the same time."

"Echoes" was nominated for the Grammy Awards' Album of the Year alongside Kanye West and Amy Winehouse. Herbie Hancock ended up being a surprise winner, but the Foo Fighters did take home Best Rock Album and "The Pretender" got Best Hard Rock Performance.

What does all the extra Grammy attention mean for the band?

"I know when we won the first time, it was a really emotional thing for everyone in the band," Mendel says, referring to a win in 2001. "We still felt like we were figuring everything out, how to write songs and make records. We didn't feel like a band on that level to even be considered for a Grammy, so it was a shock for us, and very emotional. As corny as it is at times, and there is a 'who sold the most records element to it,' but it's still flattering.

"You have this idea of a rock band from when you're a kid -- that's when you form your ideas -- and they are these larger-than-life characters and these superheroes, and here you are walking your kid in the park and you realize you're in one of these bands, and it just feels incongruous and strange -- but great. I'm happy with what our band's accomplished."