"We're like sisters," says Mary Segura, 14, a sophomore at Pioneer High School who sings bass in the group. "We get along, but we fight. Basically, it's teenage drama."

Musically, the girls are usually in perfect harmony. In the two years they've been singing together, the UnderAge Quartet has made its mark in Sweet Adelines International, performing and competing under the auspices of the barbershop organization's Young Women in Harmony program. The quartet placed third at Sweet Adelines' International Education Symposium, held last month in South Carolina. There they competed against 25 other quartets in the age-25-and-younger category. Even with this age limit, UnderAge was the youngest group to compete, and at age 13, lead singer Mia Dessenberger was the youngest performer.

Sweet Adelines singers are judged not only on how well their voices blend in barbershop harmony but on how well they use movement to explain their songs. To keep their harmonies tight and their choreography smooth, members of the UnderAge Quartet try to rehearse at least once a week.

The quartet got together after baritone Caitlin Smith, 16, and tenor Brittany Gilmore, 14, met Mary's mother, Martha Segura, at a Sweet Adelines party. After hearing them sing, Segura suggested the girls join her daughter's quartet.

"Me and Caitlin were in another quartet" at the time, says Brittany. "We didn't blend."

Segura, herself a member of an award-winning Sweet Adelines quartet, coaches the UnderAge girls. She says their young voices have developed over time.

"There's a fuller sound from all of them," adds the coach. "Once you've sung with someone for a period of time, it starts to gel and the sound gets stronger."

They may sing barbershop harmonies, but that's the only resemblance the UnderAge Quartet bears to the stereotypical image this type of musical group conjures up.

"It's not like we're in striped shirts and big moustaches," Caitlin says.

The girls choose their repertoire by "quartet vote." For their last year's IES performance, which earned them fifth place, they sang a fairly serious set. This year they sang parodies of "The Moment I Saw Your Eyes" and "This Little Piggy."

"We like to do really fun things," Brittany says.

"It's always good to make the audience laugh," Mia agrees.

All four girls have other musical outlets besides Sweet Adelines. Last year Mary was the only freshman in Pioneer's advanced choir. The other three quartet members take private voice lessons from the same teacher. Brittany sings in her church choir, and Mia and Caitlin have performed with Peninsula Youth Theatre and Children's Musical Theater of San Jose.

Brittany is the only quartet member who says she'd like to become a professional singer. Mary says she might want to teach music someday, while Mia and Caitlin say they'll probably continue with music as a hobby.

"I want to do this when I'm 60," Mia says of Sweet Adelines.

Not all UnderAge's performances are competitive. The quartet has performed the national anthem at San Jose Sharks and Earthquakes games and at the Siebold tennis open. They've also sung at each other's schools.

Despite a busy singing schedule, the girls all manage to find time for other activities.

"I play softball and hunt with my dad," Mary says.

"We all do other things, like dance," Brittany says. "We leave time to hang out with friends."

Part of the appeal of performing with Sweet Adelines is that the girls get support from older singers in the organization.

"It's like having 100 moms," Caitlin says.

"The adults really take them under their wing," says Brittany's mother, Cindy Gilmore. "Because the girls have done so well so quickly, they have a good reputation."

In October, UnderAge heads to Indianapolis for another competition. The girls get nervous to varying degrees before they hit the stage, but they always try to remember to have fun, since their next performance isn't likely to be their last.

"I figure we have many more years before we turn 25 and can't compete in this [age group] anymore," Caitlin says.