Dixie Chicks, Apollo, Manchester

Dissent still finds its focus in pop, more than any other art form. But there can have been few less likely standard-bearers for this radical tradition than the Dixie Chicks.

They played at George Bush's inauguration as Texan governor, and show no political interest in their three massively popular, mainstream country albums. But when the diminutive singer Natalie Maines declared from a London stage in March that she was "ashamed" Bush came from the Chicks' home state, corporate radio chains, the White House and red-blooded American CD-burners retaliated as if they were Saddam himself.

Death threats and the trashing of fellow Chick Emily Robison's ranch showed how costly speaking out can be. Perhaps that's why the "alternative" inheritors of rock's anti-war tradition, from The White Stripes down, have maintained a diplomatic, dim-witted silence. It only took one stray comment from a country singer to turn pop back into a battlefield.

Despite this show taking place on 11 September, on their return to the country where their troubles began, the Chicks make few initial nods to their new infamy.

Elvis Costello's "(What's So Funny 'Bout) Peace, Love and Understanding" plays them on, and Robison has a peace sign hanging from her jeans. But for most of the night, they concentrate on the musical strengths their slick albums obscure.

Though they look like small-town good girls gone politely punk, smile like game show hostesses, and mostly sing saccharine ballads written for them, the grit that led to Maines' comment is not hard to find. Robison's banjo-picking, sister Martie Maguire's fiddling and the trio's harmonising all have a fire and commitment more akin to the Nashville-loathed bluegrass revival of O Brother, Where Art Thou than the corporate country they embrace at their worst, and which has now spurned them.

"Travellin' Soldier", the Vietnam-set martial lament Maines was introducing when she criticised Bush is sung touchingly, but it's a while before her "mouth" is finally addressed. "We feel more patriotic than ever," Maguire declares, while Maines says she's "proud", as their less partisan British fans whoop. September 11, mentioned as if it's a new American holy day, introduces "More Love", a plea for peace between partners.

They don't use it to praise bin Laden, as their enemies might hope. But the strength the Chicks have discovered from being branded subversives is explained by Maines, introducing a Patty Griffin song. "I didn't know what it was about when we put it on the record," she admits. "Then when I put my foot in my mouth, it made a lot more sense."

The Dixie Chicks are more than Music Row mouthpieces now. And if Bush can radicalise their unassuming AOR, who knows where pop's war might lead next?