Christmas Rocks! : For lovers of alternative music, KROQ-FM’s benefit concert has become a staple of the season.

Jingle bells usurped by quirky Casio keyboards. Traditional carols transformed into raging speed-punk anthems.

These may not be Everyman’s idea of seasonal winter rituals, but for many concert-loving fans of KROQ-FM (106.7), alternative music and the holidays now go hand in hand.

For some, KROQ’s 7-year-old series of holiday benefit concerts, now officially called “Almost Acoustic Christmas,” has become almost as integral to the season as winter break, Christmas trees and menorahs.

A modern-day holiday sampler split into two nights of live music, the shows offer a vast collection of rock acts. And for anyone interested in taking the pulse of alternative pop music, the event--which takes place on Friday and Saturday at the Universal Amphitheatre--has blossomed into a local wintertime Lollapalooza. Past shows have included such powerhouses as Hole, Smashing Pumpkins and Alanis Morissette.

This time, Rock and Roll Hall of Famer David Bowie, the reunited Jane’s Addiction, arena-rock band Live and third-generation punks Green Day will play alongside such relative newcomers as Fiona Apple, Smash Mouth, Sugar Ray, Portishead and Third Eye Blind.

Not surprisingly, it is a frantic time of year at KROQ’s Burbank offices. A tangle of offbeat Christmas lights, CDs, modern-rock posters and youthful personnel, the bustling office looks like a cross between a business and a dorm room.

“It’s a madhouse around here,” says promotion director Amy Stevens, whose planning ranges from the logo to making sure that make-believe snow falls on fans entering the venue this year.

Because of its success, “Almost Acoustic Christmas” has spawned knockoffs by radio stations nationwide. Though KROQ program director Kevin Weatherly recognizes the competition for artist participation, he asserts that his show stands alone.

“We’ve been copied and there’s a lot of competition,” he says, “but our listeners know only one Christmas show.”

“ ‘Acoustic Christmas’ reflects where alternative music’s at each year,” says the station’s assistant program director, Gene Sandbloom, who organizes the musical lineup. “If you were to go to both nights, you would be brought up to speed on what’s going on. You wouldn’t have to go to another show all year.”

Indeed, the annual benefit has come a long way from its humble beginnings in 1990, when the then-struggling station, desperately in search of something that would boost its ratings, began tossing ideas around.

Gene “Bean” Baxter, one-half of the station’s popular morning radio duo Kevin and Bean, says that the holiday show, along with the summertime concert “Weenie Roast,” was instrumental in rescuing the floundering station. “A lot of people don’t realize that there might not have been a KROQ,” he says. “If things had gone a little worse, they would have pulled the plug.”

Though the first Christmas show sold out the 6,200-seat Universal Amphitheatre, Kevin Ryder, the morning show’s “Kevin,” says that the event--headlined by the Havalinas, Dramarama, Chris Isaak and Social Distortion--was “bad and small.” The event didn’t take off until 1992, when a surplus of bands forced KROQ to split “Acoustic Christmas” into two nights.

“With exceptions like the Amnesty International shows, Live Aid or the US Festival,” says Ryder, “you just didn’t see that many bands on a bill ever. It was the most music for the money that I’d ever seen at that time.”

Overall, the unexpected moments of past shows are the most memorable for Baxter, Ryder and KROQ fans--such as in 1993 when then-68-year-old crooner Tony Bennett, the oldest person ever to perform at the Christmas show, brought the house down for a roaring Gen-X crowd.

Kevin and Bean also remember fondly last year when Beck delighted the crowd with his version of the ‘70s dance “The Robot” and the largely unknown Fiona Apple almost walked away with the evening.

“Sometimes,” says Ryder, “certain bands come out and the electricity is just unbelievable. . . . The coolest moments have been the surprises.”

One surprise this year will be the addition to the weekend bill of a “multi-platinum” artist--to replace the ill Bjork and the Verve, which canceled following a death in the family of lead singer Richard Ashcroft. Expect the announcement on the station this afternoon.

But the main idea of the show, that it would benefit charity, has remained central to “Almost Acoustic.” This year, the proceeds will be split between Para Los Nin~os, Los Angeles Homeless Health Care, L.A. Youth Network and the Al Wooten Jr. Heritage Center.

Boosting the natural feel-good vibe of a benefit, Weatherly thinks that the time of year naturally contributes to the atmosphere onstage. “We put so much energy into the show, it’s such a great cause, we broadcast it live, and it’s the year-end wrap-up for a lot of the artists, so it’s a festive experience and most of them are genuinely happy to be part of it.”

BE THERE

KROQ’s “Almost Acoustic Christmas” concerts featuring Fiona Apple, Chumbawamba, Jamiroquai, Jane’s Addiction, Matchbox 20, Sarah McLachlan, Smash Mouth and Sneaker Pimps on Friday; the Aquabats, David Bowie, Everclear, Green Day, Live, Portishead, Save Ferris, Sugar Ray, 311 and Third Eye Blind on Saturday; Universal Amphitheatre, 100 Universal City Plaza, Universal City, 5:30 p.m. both nights. Sold out. (818) 622-4440, (818) 854-5050.