Siouxsie & the Banshees Go for a New Sound : Pop music: The band will go acoustic at a benefit concert Saturday. ‘We decided to do it because it will put us in a terrible position,’ says singer Siouxsie Sioux.

Siouxsie & the Banshees have held their position near the top of the post-punk underground for more than a decade. The group, fronted by the exotic singer Siouxsie Sioux, is a style-setting, enduring force that’s pretty much seen it all in its long, winding career.

But as the English band prepares for its headlining appearance at the Universal Amphitheatre on Saturday, it’s facing a great unknown.

“We don’t know what’s gonna happen,” singer Sioux said of the concert this week. “We’re gonna see what happens. We’re gonna be watching ourselves as much as anyone else. . . . You’ll all get a good laugh out of it one way or another.”

What has the veteran band up in the air? Saturday’s “KROQ Acoustic Christmas” benefit concert will be the first time Siouxsie & the Banshees have ever done an acoustic performance--no amps, no synthesizers, no sound effects.

Sioux said that the charity aspect--proceeds will benefit the Homeless Coalition--was a key reason the band agreed to participate. But there were other motives as well.

“We decided to do it because it will put us in a terrible position,” Sioux said.

“It’s an unknown. . . . I think that’s how we’re still excited and interested in what we do. We put ourselves in situations that we don’t know how we’re gonna get out of. I think you need to do that to yourself every once in a while.

“Just the idea of giving yourself a discipline that you wouldn’t normally put on yourself, that’s what appealed to us. . . . Hopefully, it is going to be a way of seeing a different angle on things. We’re just looking forward to it, either to trip ourselves up or find something we didn’t know we had.”

That was pretty much the idea behind the “Acoustic Christmas Concert” concept, according to organizer Missy Worth.

“I wanted to do a charity show, and we decided on the acoustic format to make it different--to have these bands show their heart, that they’re not just synthesized bands. It just shows a different side of the band that you don’t normally see in their concerts.”

Worth, vice president in talent and acquisition for the Universal Amphitheatre, started the series three years ago with a lineup headed by Camper Van Beethoven and an audience of 2,000 at the 6,000-seat theater.

Last year, an about-to-be-big Chris Isaak and popular L.A. bands Dramarama and Social Distortion helped draw a full house, and this year’s ambitious lineup--the Banshees, former Echo & the Bunnymen leader Ian McCulloch, New Jersey rockers the Smithereens, L.A. popsters School of Fish, English groups the Wonder Stuff and This Picture and the admired English singer Alison Moyet--sold out in two hours.

These aren’t just token star turns. The sets in the five-hour concert will range from 35 minutes to more than an hour, and most of the performers are coming to town specifically to do this show. All the artists are donating their time.

“I think were going to see a real warm side of all these bands,” said Worth, who has aligned her enterprise with KROQ-FM to tap the alternative-rock station’s loyal, adventurous audience.

Maybe, but Sioux warns her fans not to expect her to become a folk singer for a night.

“I’d like for it to be different,” she said. “I’d like people to know that it’s me doing it, as opposed to reverting to a role model or stereotype. I’d like it to have an edge to it.”