Something a kid with an electric guitar plugged into an amp rarely hears from an authority figure: "You need to be louder."

That's what Michelle Friedman, a band coach at Girls' Rock Camp, tells Kaitlin Turner-Simotics of Duluth, who's holding a guitar almost as big as she is. Friedman turns up the amp —- "that's as loud as it will go" —- and Kaitlin's band, the Voltz, which did not exist five days ago, plunges ahead with a loud, sloppy, fun rehearsal.

Girls' Rock Camp started in 2001 in Portland, Ore., and has spawned a documentary, a book and spinoff camps in 13 cities. Atlanta's camp is on its maiden voyage this week, heading toward its big moment, a concert tonight by the 24 girls who've been writing their own songs and rehearsing all week at Eyedrum Gallery.

Rock summer camps for teens have been proliferating in recent years, with several in metro Atlanta, but Girls' Rock Camp is the first for girls only, ages 10 to 18. Camp costs $250 for one week, and instruments are provided, although many girls bring their own.

"This is a place where these girls can come to discover their own voices," says Stacey Singer, the Atlanta camp's founder and director.

Part of that voice-finding is the camp rule that the girls have to write and perform their own songs rather than stick with familiar cover songs.

The result is new songs like "Puking Up a Revolution," a stream-of-consciousness punk ditty written, quickly, by a power trio who have dubbed their band Whateveryouwant —- Carly Pope on drums, Leslie Lang on guitar and Lily Vann-Womack on bass. At 14, Carly is the elder rocker and takes charge of rehearsal, clicking her sticks with authority as she counts them off: "1, 2, let's go!"

"It's a part of our mission," says Singer, a former bassist for local band My Siamese Self. The camp also has workshops in girls' image issues, self-defense and other topics. "Learning to play an instrument is not our primary goal," she adds.

Singer says about half of the girls knew how to play instruments before coming to camp and half are novices. Some, like 10-year-old Roxy Brown of Decatur, knew playing music only from the popular play-along video game "Rock Band."

But when she sits down behind a drum kit, with her punkish streak of green hair, no one needs to tell her to play louder.

In her foreword to "Rock 'N' Roll Camp for Girls," the new book about the growing franchise, Carrie Brownstein of rockers Sleater-Kinney writes:

"Bold is not a wanky guitar solo at Madison Square Garden that lasts five minutes while hundreds of thousands of dollars' worth of lights and pyrotechnics tell an audience when to applaud. Bold is learning to play the drums on Monday and performing in front of 500 people on Saturday."

And bold is Roxy Brown, playing her first live gig tonight.

Is she nervous? "A little. Not really."

ACTS OF INSPIRATION

Who do you love? We asked some of the campers at Girls' Rock Camp who inspires them. Some responses:

> The Indigo Girls. "They really enjoy their music and they have fun onstage." —- Wildflower Martin, 13, of West End

> Ella Fitzgerald and early Gwen Stefani. "These are my female empowerment inspirations." —- Drake Lee-Patterson of Louisville, Ky.

> Kate Pierson and Cindy Wilson of the B-52s. "They rock hard, and their beehives are fantastic." —- Carly Pope, 14, of Inman Park

> "That girl who sings 'Bang Bang' on the 'Kill Bill' soundtrack. What's her name? Nancy Sinatra!" —- Marlee Coulthard, 11, of Acworth

> Michelle Malone. "She's country, but she also rocks." —- Harlow Poteete, 10, of Decatur

> Janis Joplin. "She's just amazing." —- Rebecca Swan, 13, of Buckhead

CONCERT

Girls' Rock Camp Showcase 8 tonight at Eyedrum Gallery, 290 Martin Luther King Jr. Drive, Atlanta. Tickets: $10. 404-964-5976. www.girlsrockcampatl.org.