As the sun set on the first night of Lollapalooza, 90,000 concertgoers were forced to make a tough decision: whether to watch Lady Gaga's bombastic, elaborately produced performance at the south end of Chicago's Grant Park or nab a spot by the stage a mile away, where the Strokes would be playing their first U.S. show in more than four years. "It's sort of like the Beatles versus the Rolling Stones," said Metric singer Emily Haines, as she pushed through a throng of VIPs (Grizzly Bear's Ed Droste, Dirty Projectors' David Longstreth and Ke$ha among them) clamoring for a side-stage view during the Strokes' set. "We decided, as a band, this is where we need to be."
For Gaga, Lollapalooza was just another stop on her extravagant Monster Ball Tour – same set list, same pyrotechnics, same fountain that spews blood. It was the kind of thing you just had to see. But after a few songs, a large portion of the crowd started migrating north for a performance that had a true sense of rock & roll danger. "I've never been to Lollapalooza before, but it's my new favorite festival," said Strokes frontman Julian Casablancas, addressing the attendant mass. "Land of dreams, where Nirvana and Pearl Jam did all their shit."
The Strokes' set was bold and simple, with minimal stage adornment. Blasting off with fan favorite "New York City Cops," the band powered through a tight 16-song set, ranging from a beautiful, scaled-back rendition of "Under Control" to an electrifying "Heart in a Cage," during which Gaga's fireworks – visible over the trees from across the field – seemed like they belonged to the Strokes.
The sixth annual Lollapalooza felt like the tale of two festivals, as each night's headliners divided the park between the more mainstream Parkways Stage (Gaga, Green Day, Soundgarden) and the edgier Budweiser Stage (the Strokes, Phoenix, Arcade Fire). If that contrast was part of a deliberate strategy by promoter C3 Presents, it worked. This year's event drew Lollapalooza's biggest audience ever, with more than 240,000 tickets sold over the course of three days. "I've never been so fucking nervous," said Black Keys drummer Patrick Carney, drenched in sweat, moments after playing to the massive crowd.
"What I dig about Lollapalooza is just the variety of bands that are playing, and the quality of bands," said B-Real of Cypress Hill, who played on the closing night. This year's 152 acts on eight stages ranged from superstar DJs (Kaskade, 2ManyDJs) and buzz bands (Wavves, Mumford and Sons) to contemporary R&B (Raphael Saadiq, Erykah Badu) and classic acts (Devo, Jimmy Cliff). Early on Day One, 71-year-old Mavis Staples lit a fire under the sleepy crowd by bringing out her fellow Chicago native Jeff Tweedy, who accompanied her on his beat-up acoustic for "You Are Not Alone" – a song he penned for the upcoming Staples LP he produced. "I've been singin' a long time," said Staples, drinking iced tea backstage. "The way these young people responded makes you feel really good. I'll be grinning tonight in my sleep, if I get to sleep. I'm wired up now!"
Lollapalooza-goers settled into a mellower groove on Saturday, particularly at the Sony Bloggie Stage, set in a shaded nook on the edge of the park. Los Angeles four-girl band Warpaint's swirling, woozy tunes and roots-rock group Deer Tick got folks off their blankets and onto their feet. "My ultimate goal is to go to the hotel pool at the Hilton and then see Green Day, hell yeah," Deer Tick singer John McCauley said, as the band closed its set with an eight-minute version of "Mange."
But the afternoon belonged to Edward Sharpe and the Magnetic Zeros, who rallied a huge crowd with an emotional hour of music that had fans climbing the trees for a better view. During a set-closing performance of "Brother," frontman Alex Ebert walked into the middle of the crowd and sat down. Within moments, the audience had quietly followed his lead – sitting down one by one until the whole field was cross-legged on the ground.
Following powerful but restrained performances by Grizzly Bear and Spoon, Saturday night's Phoenix set at the north end of the park epitomized the Budweiser Stage's emphasis on subtlety over glitz. "It's great that people have to choose between us and Green Day," Phoenix bassist Deck D'Arcy said sarcastically. "Because the choice is very easy." Across the park, Green Day pulled out all the stops. While reaching back to early songs such as "Paper Lanterns" to tracks off 21st Century Breakdown, Green Day gave the fans everything they wanted – including T-shirts shot out of a cannon and an ecstatic medley of "Shout" and "Hey Jude." "They keep telling us they're gonna pull the plug at 10:00," yelled Billie Joe Armstrong. "You know what I say? They can kiss my fucking ass – we're gonna play as long as we want."
Although the final day began with rain, the sun came out for an epic set by MGMT that mixed the psychedelic material from this year's Congratulations with Oracular Spectacular favorites like "Electric Feel" and "Kids." "For a long time, I felt like we kind of sucked," guitarist James Richardson said, puffing on a joint backstage. Added singer Andrew VanWyngarden, "This is the best we've sounded since we started."
Sunday night, old-school alt-rock fans and their new-school counterparts split the field in half – the former packing the south stage for Soundgarden's first official reunion concert while the latter staked out spots on the opposite end of the park to hear Arcade Fire play material from their new album, The Suburbs.
You couldn't go wrong either way: Soundgarden sprayed reverb across the packed crowd as they played a rare full-band version of "Black Hole Sun" and closed their set with a 10-minute jam on "Slaves and Bulldozers" before leaning their guitars up against their amps and walking off to the screeching sound of feedback.
Arcade Fire closed the festival with an explosive set that included seven tunes from The Suburbs. "It's intimidating playing new songs in front of such a huge audience," admitted frontman Win Butler. But by the time they wrapped with a singalong on the U2-size anthem "Wake Up," Arcade Fire had proved that huge audiences are officially the band's new purview. It was a moment, like so many at Lollapalooza, that lived up to what the National's Matt Berninger described as his own band's ultimate goal for its Sunday night set: "There's a sort of chemistry that happens sometimes at these festivals – those weird moments when the crowd just feels like one organism, and you feel like the brain."
This story is from the September 2nd, 2010 issue of Rolling Stone.