Shut Up & Sing wants to give us a backstage pass to a publicity crisis, but the more interesting story that shines through is about the enormous power that even a travel-sized lead singer can wield over a band. The story begins in 2003 when Natalie Maines, the frosted blonde frontwoman of the Western swing-pop threesome The Dixie Chicks, makes an off-the-cuff to a London crowd about being embarrassed by Bush. The insult bounces around the globe, lands on redneck radio and results in a sturdy boycott that sinks plans for a tour. Maines is urged to back-peddle. Instead, she tries to spin the 'traitor' label into a new, quasi-edgy image for the hitherto-wholesome group. For fickle fans, it's a bridge too far. "You're giving the American public too much credit," her publicist warns. Meanwhile, the other Chicks fume. Fiddle player Martie Maguire wants to chick-scratch Maines' eyes out for gambling with their careers. At one point, in a moment that's almost off-camera, she mumbles: "I'm not gonna try to dig you out."

But Maines knows she is irreplaceable -- the Chicks opened supermarkets before her -- and she doesn't sweat vague threats of ouster. Everything she does, from the way she interrupts meetings with daydreamy musings to her snap decision to cut ties with a wavering sponsor, exposes her as the group's 800-pound gorilla. The film's best moments occur when she pipes up with an opinion, and the other Chicks bite their tongues. As the pressure increases, Maines begins to flirt with severing the group's connection to country music, which she's not culturally wedded to. This leads to a hilarious scene where she drags the other Chicks to the Maharishi-like pad of music impresario Rick Rubin for a musical powwow. Maguire, who was baptized in bluegrass, not Beastie Boys, is lost at sea. She eventually blurts out "What is our role?," prompting Rubin to make a cryptic statement about finding the best sound, 'whatever it may be'. He probably said that to several Chili Peppers drummers before they were axed.