You don't get a "show" at a Fleet Foxes gig. There are no inflatable bats, no leather-clad singers on motorcycles hurtling into the orchestra pit. Their between-song patter consists of excruciating tune-ups, beards quivering as they exchange knowing glances and mutter – presumably – about guitar strings. But they get away with it because the music is so astounding.

Even if you're familiar with last year's acclaimed debut – as 99% of this audience certainly are – it's still astonishing how the Foxes transform an uncomfortably busy black hole into a magical grotto. Several times, thousands of lairy Geordies are stunned into silence by the band's three-part harmonies and hymnal psychedelic folk: something like Simon and Garfunkel and the Beach Boys jamming in an 18th-century church.

With percussionists driving the music on like jockeys whipping a horse with maracas, the "performance" arrives in subtle touches. During a solo section, singer Robin Pecknold feigns surprise that his band have left him alone with a guitar, but shows he could have had a mighty fine career as a singer-songwriter had he not joined a band whose sound relocates 1967 hippy to 2009 Seattle.

As album highpoints White Winter Hymnal and He Doesn't Know Why tumble forth, along with lyrics about "shivering dogs" and "quivering forests", someone makes a comment about Pecknold's beanie. "My hair's between long and short," he explains. "I can't do anything with it." "Off! Off! Off!" cry the crowd. He duly removes the hat, and everybody cheers as if they've just seen an inflatable bat.