Band of Horses, Koko, London

No angst: Band Of Horses' singer Ben Bridwell © Stephen Lovekin/Getty Images

When a hip young Seattle band on the verge of success tell an interviewer their ambition is "to not be a shitty indie-rock band ever again", you know there's a change in the air. Just as once-quirky Britpop has become the mainstream, so have sharp-witted US rockers such as Band of Horses.

Seeing their singer Ben Bridwell, trucker's beard and cap more visible than his face, it's no surprise to hear the Seventies rock classicism that gave Midlake success. But his giant, echoing falsetto owes more to My Morning Jacket's Jim James, and Neil Young, all three's common root.

Yet, for all the Memphis horn-blasts from Ryan Monroe's synths, Band of Horses (from South Carolina before Seattle) aren't mere Southern retro. Their defiantly big sound carries echoes of Eighties UK indie's most ambitious bands. "Ode to LRC" may be about a dog Bridwell met in a backwoods bar, but when the guitars drag back and the drums tumble down, its post-punk jerkiness twists otherwise straight country-rock. Think the Bunnymen, down at the crossroads.

Because Bridwell shows no angst on stage, and the music sounds triumphant, his troubled yet beatific lyrics don't stick as they might. "Pretty sensitive, huh?" he gently mocks after "No One's Gonna Love You", a big, crafted ballad about a relationship "splitting at the seams". Though Iron & Wine apparently spurred them into Americana, Bonnie "Prince" Billy is buried in the consideration of evil in "Wicked Gil". On that and "Marry Song", I wish Bridwell's reverb-drenched falsetto would switch off, like a superhero reverting to civvies, to hear them straight; the constant grandeur wears thin.

"The Funeral", their 2006 success, stands out by starting with lonesome voice and guitar, before the band blast back: Cobain's old Seattle quiet-loud dynamic and morbidity remade as Southern gothic. Near-hits this weirdly majestic are rare.

Bracingly played cover versions explore Band of Horses' roots. Creedence Clearwater Revival's "Effigy", with its images of burning countryside scourged by "the silent majority", resonates with 1969's counter-culture struggles; they only catch its apocalyptic musical sense. They must dream of JJ Cale's "13 Days", about a rock tour through the Seventies South, every day, while the Keith Richards obscurity "Act Together" tries Stonesy raggedness.

Their own "The General Specific", pure Southern Americana with boogie piano, nearly matches it. But their swagger is stiffened by UK dilutions. This London crowd love them, and they leave looking grateful. But more light and shade is needed in their glaring bid for success.