When people go see a Bouncing Souls show, they have a pretty good idea of what they're getting.

On the other hand, the band plays punk rock, so it's hard to say exactly what will happen when it takes the stage 7 p.m. Sunday at the Cell Block, 420 E. College Ave.

"When you get a bunch of people in a room with a bunch of loud, fast music, anything can happen," bassist Bryan Kienlen said.

Still, in the 20 years the band has been playing together, there have been few drastic changes. In fact, in that time, there has only been one lineup change.

Drummer Michael McDermott, the one change, said the band's biggest accomplishment, aside from simply staying together for two decades, has been finding and maintaining a unique sound.

"For us," McDermott said, "the music now shows we've been a band for 20 years. If you have a brain, you're going to evolve, but we're still the Bouncing Souls, and we've never really waned from our sound."

Though the set list for Sunday's show will surely include staples like "True Believers" and "Hopeless Romantic," McDermott said nothing will be really predetermined and the Souls will respond to a lot of requests from the audience members in attendance.

"We're not even really on a tour," McDermott said, as the band is only playing a string of six shows. "It's really just whatever hits us that night," he said.

Such spontaneity, however, can be problematic for the Souls while playing a set.

McDermott said that because two of the band's songs have similar beginnings, guitarist Greg Attonito will sometimes start one and end up playing the other, even if the rest of the band is playing something else, and sometimes it takes him three or four tries to get it right.

"I'm not sure other bands would keep trying to play the same song if that happened," McDermott said.

Regardless of what happens on Sunday, Kienlen is sure it will be a good show.

"Everything involved with the Bouncing Souls is fun," he said. "We're drawing this stuff from inside ourselves, so it's one-of-a-kind."

At the very least, the band is different from the other bands that have played and will be playing at the Cell Block this semester.

"We want all our shows to be all different genres," general manager Joe Yamma said.

Already, the Cell Block has hosted or plans to bring four decidedly different acts to the venue.

Blues-rocker Robert Randolph and punk-pop band Yellowcard came this fall and tickets are currently on sale for alternative metal acts Trapt and Drowning Pool.

Yamma said he is booking shows based on what had been successful at Crowbar, but he is also looking for direct feedback from State College concert-goers.

He said anyone can offer suggestions for shows they want to see via the Cell Block's MySpace and Facebook pages.