Using interviews with the girls, parents and counselors, Girls Rock! is as much about the self-confidence issues young women face as it is about music: Misty is a 17-year-old who struggles to shake her past life of drugs and crime; Amelia is only eight but writes art-punk songs dedicated to her dog; Laura is a teenage death-metal fan who always feels like an odd girl out and has trouble finding likeminded band mates, adding to her already low self-esteem.

King says Girls Rock! has gotten raves from young girls and their mothers but also strikes a proverbial chord with other demographics. “We wanted to tell the most interesting story we could about what was going on at the camp,” King says. “I’m a 40-year-old man, but I think it’s an engaging and interesting story, so I think it’ll definitely appeal to a wide audience. I feel like I have gone through the transformation that a lot of the girls went through.”

In addition to Chicago, rock camps have been launched in Memphis, San Francisco, and Austin. Emily Easton, camp director of Girls Rock! Chicago (which was founded in 2005) says the Portland camp experience portrayed in the film is very similar to the one she sees here. For Easton, the film shed light on ways the Chicago camp can grow, too. “I’d really like to see more of the girls here using their voices [as musical instruments, like they do in the movie], even if they are just screaming,” she says. “Like a girl in the film said, ‘Women don’t really tend to be loud, and you’ve got to get it out there.’ ”

Easton would also like to add a counselor jam session like the one in the movie. “That was really inspiring to me,” she said. “I can’t even imagine how much more [exciting] that would be, seeing that when [you’re] nine years old.”

The film ends with the girls performing in front of 700 people. Their musical transformations are evident, but their individual abilities to work in groups and the growing up they do over the course of the film are the most moving, Easton says. “It’s an awesome experience, no matter where it is,” she says, noting that 60 of the 2007 Chicago campers enjoyed their summer so much that they are returning when camp begins again this August. (Applications for the remaining 12 spots will be available soon at girlsrockchicago.org.)

Just as in the film, Easton says, Chicago parents are usually in tears watching their daughters perform at camp’s end. But you’d be surprised at who’s most teary-eyed: “It’s usually the dads,” she says.

Girls Rock! opens at the Music Box Theatre on Fri 7.