CHICAGO Lollapalooza opens its 20th anniversary bash

This was one rocking birthday party—and it's only just begun.

Lollapalooza, the iconic, trendsetting music festival established and fronted by Jane's Addiction's Perry Farrell, kicked off its 20th anniversary celebration Friday at Chicago's Grant Park, where its been held annually since 2005, with an expanded 115-acre layout and a sold-out crowd of 90,000 people. News that another Lolla will debut next April in São Paulo, Brazil was announced, the second foreign incarnation after a Santiago, Chile version launched this year.

From buzz bands to big names: On Friday the first wave of 130 acts hit the stages from Foster The People and Cults, to British headliners Muse and first-time Lolla act Coldplay. The other rockers, rappers, pop stars, soul singers and DJs, are slated to perform by 11 p.m. ET Sunday.

Weather to rock by: Neither high humidity nor rain crashed the party, at least on Friday. Temps stayed in the 80s, and rain stayed away, making for pretty optimal fest weather that's expected for the rest of the weekend.

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Following in Dad's footsteps: Rock is literally in Adrian and Tony Perry's blood; the two siblings behind four-piece TAB the Band, one of Lolla's opening acts Friday. They're the kids of Aerosmith guitarist Joe Perry. Singer Adrian and guitarist Tony showed they could work a stage like the old man, but they did it on their terms with a decidedly different, slightly Southern, indie garage rock sound. Sure, having a Dad in Aerosmith doesn't hurt the guys' chances of stardom, but with strong material like One of Me, with a chopper-like guitar riff and Adrian's interchangeably longing, lustful delivery, TAB is a good band in its own right, regardless of lineage.

Shameless self-promotion: The Vaccines' singer Justin Young was so adamant about promoting his buzz band he wore a Vaccines shirt to their set. But the British band's music, most closely resembling The Jesus and Mary Chain, remained the strongest-selling point of the early afternoon. Young consistently sang from his moccasin-enclosed tippy toes, at one point channeling Buddy Holly-style swoon on Wetsuit." This wasn't rip-roaring festival music, but Vaccines at least backed its buzz.

Pumped-up kid crowd surfs to Pumped Up Kicks: And the winner of Lollapalooza's unofficial wet shirt contest goes to Foster The People's Mark Foster. Hewasn't even halfway through the band's mid-afternoon show and his white shirt was already so soaked from sweat it was translucent. A respectable cover of Neil Young's classic Heart of Gold drew some appreciative cheers from audiophiles. But it was People's own ultra-cool, mover and shaker Pumped Up Kicks, one of this summer's biggest breakouts, that sent the crowd into shrieks and spirited signing. Crowd surfing picked up with the enthusiasm; amongst those riding the masses were a guy dressed in a watermelon costume and 12-year-old Pat Williams. Not to worry parents, the boy was safely grabbed by security. "I wasn't scared," Williams said moments after his feet returned to terra firma. "That was my second time [crowd surfing] at this show. I love this band." And with that, Williams skipped right back into the pit to rock some more.

A big break in their backyard: The year Lollapalooza was born, Cameron Omori, the lead singer of rising glam rockers Smith Westerns and his brother, Cullen, were just a year old. Flash forward to Friday, the brothers and bandmate Max Kakacek performed on stage. "Within the course of this year, people started appreciating our music, and I think it kind of came to a head at Lollapalooza, in our hometown," Cullen said. "It's kind of surreal that in 2011 we're playing here whereas in 2006 we were out in the crowd."

Co-ed tag teams: One recurring theme at Friday's Lollapalooza was guy-girl tag teams, although the various pairings couldn't sound more different.

The Kills' guitarist Jamie Hince laid down dense, intense indie rock riffs as body-whipping Alison Mosshart sang sultry vocals through a weave of sticky, jet-black hair. When her eyes peered through on tracks like pulsating Heart is a Beating Drum, off its album Blood Pressures, Mosshart looked like a tiger poised to kill its prey.

On the opposite end of the spectrum, playing at the same time, retro pop revival act Cults, expanded from duo Madeline Follin and Brian Oblivion to five touring performers. Their gentle, xylophone-kissed, '60s pop-leaning instrumentation gracefully glided over the crowd like a fluffy cloud, masking many of the tracks' melancholy lyrics, and making up for the fact that standout Go Outside lost some context out in broad daylight.

Somewhere in between the intensity of The Kills and the lightness of Cults was Black Cards, a new duo (expanded to include a drummer for Lolla) created by Chicago-area native Pete Wentz while emo-pop juggernaut Fall Out Boy is on indefinite hiatus. Unlike Kills or Cults, Cards is electro pop through and through, led by newcomer Bebe Rexha on vocals. While the music was light in tone, the performance was as aggressive a spectacle as you could get from a band with its first album still in the wings and performing on one of Lolla's smallest stages. Rexha exuded confidence and chops singing wannabe club jams like Take Me Down (Higher), released on SoundCloud the day of the show. She was joined on stage by dirty dancing models in skimpy black outfits initially wearing werewolf masks, a freaky, arm-twisting, head-popping contortionist, and Wentz, who threw beach balls and toilet paper rolls into the crowd, and stagedived three times in less than 30 minutes. "I just wanted to have fun on stage," Wentz said. Based on the crowd's reaction, the fun was infectious.

A Perfect Circle's latest: The band was a perfect choice for Lolla goers in the mood to brood. Not that the alternative metal act, featuring Tool vocalist Maynard James Keenan and former Smashing Pumpkins guitarist and Chicago native James Iha, didn't display superb, guitar-driven, melodic musicianship. It also displayed new track, By and Down that's made the rounds on the band's summer tour, but has yet to be released as a single or on an album. It features some of APC's most poetic lyrics to date, and an exceptional guitar build-up that releases into atmospheric keyboards.

Bigger Perry's stage isn't big enough: The biggest addition to Lolla this year is the expansion of the Perry's DJ stage to a tented venue with a capacity of 20,000. But within a few hours, it looked like Lolla organizers would have to increase capacity already next year. People were packed in shoulder to shoulder, with thick clusters around the perimeter, waiting for Afrojack to take the stage. It was so crowded, the Chicago Fire Department briefly delayed the show until some space was cleared. And Afrojack wasn't even the stage's final headliner (that honor would fall to Girl Talk). "We are sliding on sweat," Nicole Mendoza, 18 of Chicago, said of the conditions inside.

Hot show by Coldplay: The stars warmed up their crowd with an unexpected performance of Jay-Z's profane 99 Problems inspiring thousands in the crowd to sing along. But don't fret, Coldplay is still Coldplay, devoted to thematically safe, nevertheless ambitious anthems that stir the emotions. That applies to the five songs Chris Martin and company played that have already made the rounds at some summer shows in Europe. Standouts included Charlie Brown, with Jonny Buckland's sticky, uplifting guitar work, and the soft, romantic Us Against The World, which featured drummer Will Champion on piano and backing vocals. The masses seemed engaged with the new stuff, but it showed the most enthusiasm with familiar favorites, singing loudly to Yellow, In My Place and The Scientist. Before Martin had a chance to sing a single note during a long intro to Viva la Vida, fans were already singing the lyrics. The band also explored some creative liberty on God Put a Smile Upon Your Face, rearranging the intro and incorporating galloping drum work. "It took us 20 years to get to Lollapalooza and we've always wanted to do it," Martin said. "Thank you for making four young, well not that young anymore, but four men's dreams come true. We're going to give everything we have this evening." Coldplay lived up to his word.