MUSIC : Are The Edlos really out of this world? : Norris Theater audiences can be the judge.

There are at least two stories behind the birth of The Edlos, the self-proclaimed “bad boys of a capella.”

One legend has it that four aliens from the planet “A” (which circles the star Capella) are kicked off their planet for singing too loudly. The Edlos (Excessive Decibel Levels from Outer Space) are exiled to outer space but their starship crash-lands in 12th Century France. There, the refugees kill off four friars, sonically clubbing them with discordant music, and take over their human bodies. They become immortal and travel the centuries, meeting music-world luminaries and getting into trouble.

According to the other story, four Bay Area performers “saw the light” after spending a decade performing professional opera. The singers hit it off one night in 1989 while singing a capella (without instrumental accompaniment) at a cast party, entered a competition or two, racked up some awards and took their show on the road.

South Bay audiences can probably find support for either legend when the opera renegade/aliens present their satiric show at the Norris Theatre for the Performing Arts on Sunday at 8 p.m.

“It’s wonderful just to listen to their music,” said Michelle Roberge, Norris spokeswoman. “But they’re wacky and irreverent and hysterically funny. . . . They’re a thinking man’s band.”

The two-hour program highlights the group’s vocal versatility featuring everything from Gregorian chants to barbershop and contemporary pop favorites. But the sassy quartet uses outlandish costumes and comic ad libs to put new twists on music from the 1930s through the 1980s, including “Mood Indigo,” “Unchained Melody,” “Lion Sleeps Tonight” and “Moondance,” said agent Ralph Pavone.

The classically trained singers--two members studied at the San Francisco Conservatory of Music--make good use of their education, Pavone said. Their dramatic approach to the material reflects their opera background. The power, beauty and technical acuity of their voices is not always found among a cappella performers.

“What’s different about these guys is that they use their operatic roots and, unlike other a capella groups, they don’t just stand at the microphone,” Pavone said. “They’re very theatrical.”

The group tours the country performing at colleges, festivals and performing arts centers. They’ve self-produced three albums and have shared the stage with performers such as Ray Charles, Bernadette Peters, Crystal Gayle, The Temptations and Chicago.

But it is original compositions such as “Opera Rap,” “Gimme a Break (or the IRS Blues)” and a “Down at the Mall” that provide most insight into The Edlos attitude. The group even wrote a number that recounts the 1989 San Francisco earthquake from a cat’s perspective.

Sometimes audiences are not quite prepared for the group’s “bad boys” playful attitude, Pavone said.

“People sit there and go ‘What the hell is this?’ but they figure out it’s all tongue-in-cheek,” Pavone said. “These guys are all a little strange. Nobody ever forgets them once they’ve seen them.”

Tickets are $22. Group discounts are available. The Norris Theatre is at Crossfield Drive and Indian Peak Road in Rolling Hills Estates. Information: (310) 544-0403.