For the first time since it began in 1999, organizers have scheduled the three-day festival for two consecutive weekends with identical lineups, highlighting its growing popularity.

But recreating the experience two weeks in row has provided a challenge for organizers because fans go to festivals for unique experiences where one never knows what will happen.

In 2008, one of Pink Floyd's giant inflatable pigs "escaped" its tethers on the stage and floated off into the desert, sparking a pig hunt that made headlines around the world.

More important, Coachella has become a proving ground for young bands looking for a big break who might do just about anything on stage, as well as established acts wanting to cement their fame among the mostly young music lovers who turn out for the shows near Palm Springs, California.

"Coachella has pushed boundaries in the past. It has redefined what festivals are about, and has a different character to other festivals around the world," said Tye Comer, editor of Billboard.com, to Reuters.

He acknowledged that this year there is a "fear that it's going to be a bit tainted for people going the second weekend because they're getting a copy of the first weekend."

One factor that may divide the two weekends, however, is the weather. Early forecasts show a chance of rain and cool winds during the first weekend -- a far cry from the typically hot, sunny, desert weather. That threatens to turn the first weekend into a mud bath, whereas the second will likely be clear and dry.

But the festival needed to expand to handle the crowds, and tickets for both weekends are sold-out. Coachella has grown from 25,000 attendees initially to 75,000 people a day over the three-day weekend, and it has become an important platform for rock, rave and electronic music acts such as Daft Punk, Rage Against The Machine and The Mars Volta.

DR. DRE IN THE DESERT

The diversity in this year's three headlining acts - American rockers The Black Keys on Friday, Brit-rock band Radiohead on Saturday and hip hop veterans Dr. Dre and Snoop Dogg on Sunday - highlights the growing fusion of genres consumed by the mainstream audience.

Sunday's rare performance from the reclusive Dr. Dre has fans and critics buzzing with speculation that rappers Eminem, Wiz Khalifa and Warren G might join him and Snoop Dogg as surprise guests.

"It's what makes Coachella so unique because you won't see Dr. Dre and Snoop performing at Lollapalooza or Bonnaroo. Coachella's really good at going back 20 or 30 years, finding artists and pulling them back onto the main stage," Comer said.

Radiohead returns to Coachella for the first time since blowing crowds away with their 2004 performance - the first year the festival sold out in advance. The Black Keys make their transition from alternative rockers to headlining act, after performing at the festival many times in the past decade.

Newcomer acts also have the opportunity to break through the clutter of bands with a stellar performance. This year, Belgian artist Gotye, electro-pop French musician M83, Harlem rapper Azealia Banks and New Orleans neo-soul singer Frank Ocean, are expected to be ones to watch at this year's festival.

Beyond the music, Coachella is known for its buzzing party scene as young Hollywood celebrities and artists indulge in pool parties and nighttime events set up by brand sponsors at private estates and hotels in the Palm Springs area.

This year, Filter Magazine is holding its annual yacht club party, designer brand Mulberry dishes out barbecue by the pool, and Belvedere Vodka's music lounge promises surprise guests and music acts lined up to perform.

(Reporting By Piya Sinha-Roy; Editing by Bob Tourtellotte and Jill Serjeant)

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