There is no instruction manual for being a rock star. There is no playbook charting the progression from garages and basements to clubs, theaters, arenas, sheds, stadiums and enormous outdoor festivals.

If such a book existed 15 years ago, Nate Mendel probably would have devoured it.

If the book came out in the next few months, he could contribute a chapter or two -- especially the parts about playing huge venues.

Mendel is the bass player for the band Foo Fighters, which is the featured attraction Friday night during Harley-Davidson's 105th anniversary celebration. Foo Fighters headline the outdoor venue dubbed "The Roadhouse at the Lakefront," which actually is a big patch of real estate just north of the Milwaukee Art Museum. Three Days Grace open the evening before a crowd at least twice the size of a typical arena crowds.

While such gigs are hardly unusual for Foo Fighters, an internationally popular band with a massive following, Mendel said it is not "old hat.

"I grew up in the desert of eastern Washington State," Mendel said during a recent phone interview. "When I got into music, my favorite bands played to 150 people in clubs. It's pretty much completely different than (shows like) this.

"In '95, when we first started playing festivals, I had never seen that many people before. It was a bit terrifying at first."

In June, frontman / songwriter Dave Grohl and Foo Fighters played a pair of shows at Wembley Stadium in London, where they rocked crowds approaching 90,000.

"Those shows were incredible -- the biggest shows we've done," said Mendel, who left Sunny Day Real Estate to join Grohl's group. "We had a lot of big shows this summer, but our band has always been more popular in Europe than in the U.S. Every time we go over there, it's kind of a band holiday."

The show this week will represent a "biker holiday" as thousands of Harley fans head to the lakefront in search of cold beer and entertainment.

"I don't know how to read this one," Mendel said. "Since it's a Harley-Davdison crowd, maybe we'll play all rock stuff and keep the quiet acoustic stuff down to a minimum so they don't throw bottles of piss at us.

"But, maybe they'll be into it. We'll have to decide what we're going to do. I don't know which way it will go."

Given the level of success that Foo Fighters has achieved, along with the band's history of mocking the popular Mentos commercial in a video, cynics may be inclined to sneer "Sellout!" over the group playing under the Harley-Davidson banner.

Mendel doesn't see it that way.

"The Harley-Davidson culture has crept into our band a little bit with some T-shirts," he said. "Dave (Grohl) is into it. I'm kind of the odd man out because I'm into motocross and dirt bikes...

"But, I don't see this as a typical corporate show. It's more like a whole lifestyle celebration. Those folks (Harley enthusiasts) are notorious for throwing good parties. It's going to be interesting to see how it goes."

Grohl, the former drummer for Nirvana, has written a slew of radio-friendly rockers ("Best of You," "Everlong," "My Hero" "Times Like These," "The Pretender") that can captivate a stadium crowd. In early albums, he did a lot of shouting. Lately, though, he's shown more nuances both vocally and in terms of songwriting themes.

''In a songwriting sense, Dave has evolved," drummer Taylor Hawkins told the Denver Post in a recent interview. "His lyrical content has become a bit more direct and personal, and the song structure and arrangements have gotten a little broader and more interesting.''

Again, that growth, which is evident on the nearly year-old "Echoes, Silence, Patience & Grace," is a condition that can make once-fervent fans scream "Sellout!"

"The important thing for us to make records and songs are good," Mendel said. "The feeling within in the band is that we're getting close. We feel like the best record we can make is getting close."

Though the band seldom writes during tours, Mendel said the group has "half a record" in the can. "Usually, we have about 30 songs and use about 10," he said with a laugh. "So, we'll see what happens.

"Right now, the bulk of the touring behind this record ('Echoes, Silence, Patience & Grace') is over. Everyone is relieved. We're looking forward to not doing anything for six months."

First, however, there is the Harley-Davidson show, which will be followed by shows in Toronto, a couple at Red Rocks outside of Denver and a slot at the Austin City Limits festival.

"We're always working to make our live shows better," Mendel said. "We started in clubs and moved up to arenas and it's a learning process. It changes every step up.

"It's a whole other challenge doing (big outdoor) shows. You feel a responsibility to compensate for the size of the venue. I know Dave (Grohl) does.

"You have to try to project to people more and you have to play to the (TV) cameras. It's weird. You run into a problem of it being just a TV show for the people in the back. One thing we do to combat the size is to have a second stage in the middle of the venue with a ramp. Dave goes back and forth. We do an acoustic segment out there and all of a sudden the people with not-so-great seats have great seats."

When the show ends, many in the audience will be sitting on motorcycle seats. At the time of the interview, Mendel wasn't sure whether the band's payment would include new motorcycles.

"That would be pretty good swag," he said. "Can you make that happen?"