Saturday evening at the last and finest mini-festival of late summer, and Minnesota’s most rock’n’roll Mormons can no longer turn the other cheek. Grinding to a halt between glacially slow riffs, LOW guitarist Alan Sparhawk makes an extraordinary appeal for audience sympathy.

“It’s been a crappy day,” he grimaces, voice croaking. “All the people I love told me they hated me today.” Sparhawk’s wife, drummer and co-vocalist, Mimi Parker, shoots him a look of pure poison. “Not all of them,” she hisses.

Welcome to End of the Road Festival 2008. Great sounds, magical location, and simmering marital tension live onstage. Only in its third year, Britain’s premiere one stop shop for outdoor indie-folk and left-field Americana is already an established brand and sold-out success story.

The setting is idyllic, a peacock-patrolled Victorian pleasure garden overlooking Madonna’s country estate on the verdant uplands between Wiltshire and Dorset. The musical menu may be pretty single-minded, but it is full of rewarding oddities.

Backwoods heartache chronicler BON IVER, for one. Wisconsin’s Justin Vernon proves himself worthy of the extravagant praise lavished on him this year with a warm and, given his debut album’s introverted mood, surprisingly lusty folk-rock set.

MERCURY REV headline on Saturday, road-testing the Coldplay-tinged sparkles of their new “Snowflake Midnight” album. There is too much blustery bombast in their spangled set, but at least they bring a welcome blast of awestruck cosmic yearning to a weekend heavy with prosaic beard-rockers.

AMERICAN MUSIC CLUB are engaging, but not wholly convincing. Mark Eitzel may be a sage-like poet and mordant wit, but his rambling jazz-rock confessionals seem a little smug and self-absorbed here. In baggy trousers and pork-pie hat, he could almost be fronting one of those unfathomably popular Middle American fratboy bands, like Smash Mouth or Bowling For Soup.

Sunday night headliners CALEXICO also disappoint, never quite getting into the guts of their potentially rich mongrel mix of saloon-bar Americana and Mexican mariachi sounds. Admittedly the spaghetti western trumpet fanfares sound fantastic after a guitar-heavy weekend, but most of their set is too polished, too clinical, too Crowded House.

Thankfully, End of the Road also features plenty of lesser known artists prepared to spike and twist the alt-folk rulebook. Such as the wry Canadian collective WOODPIGEON, who sound like Arcade Fire without the triumphalism. Or sardonic New Yorker JEFFREY LEWIS, who punctuates his DIY clatter with sharp comic monologues.

Meanwhile, San Francisco punk-folk duo TWO GALLANTS are plain electrifying, howling their noir-ish vignettes in a semi-feral whine pitched somewhere between Jacques Brel and prime-time Violent Femmes. More than anyone else this weekend, they sound wired, possessed and potentially dangerous. End Of The Road may be the most mellow and uplifting fresh-air festival on the calendar, but a drop of the dark stuff still goes down a treat.

STEPHEN DALTON