West along the coast is the ancient market town of Rye; to the east, Derek Jarman’s driftwood garden fossilises in the shadows of Dungeness power station; between the two, a short walk from the crazy-golf course, lie the utilitarian chalets of the Pontin’s holiday camp in Camber Sands, East Sussex. Last weekend its family-fun facade was lowered as it experienced a visitation from the New York art-punk legends Television, who had re-formed to top the bill of the most culturally significant British pop and rock festival of the year.

Two glamorously faded ballrooms that usually host knobbly-knee competitions rang instead to free jazz and stooped experimental rock bands during the most exciting weekend it is legal to enjoy at an English seaside resort. “It’s a very special experience to play here,” said Ira Kaplan, of New Jersey’s Yo La Tengo, archly to the audience. “When we were kids, my parents would fly us here from New York to holiday at Pontin’s, sometimes two or three times each summer.”

The third annual All Tomorrow’s Parties (ATP) sold out its 3,000 places in record time. Confused visitors crossed the Atlantic or travelled from Scandinavia with £100 tickets for three days’ chalet accommodation and a bill so daring it should change the sorry way music is promoted, programmed and consumed in this country for good. The absence of flooded chemical toilets, mud and Ocean Colour Scene made it seem as if there really is no reason why rock festivals must be rubbish.

This year, the booker Barry Hogan, whose ATP website mixes disciplinarianism with fan-boy wonder, asked Chicago’s Tortoise to curate the event. The 22 acts selected – including the widescreen country-rockers Calexico, the spangle-suited Sun Ra Arkestra, noisy instrumentalists Rick Rizzo and Tara Key, and the Boards of Canada boffins – reflect the band’s open-minded approach, as heard on Tortoise’s latest album, Standards (Warp).

Plucking players from local groups in the early 1990s, Tortoise could only have emerged from Chicago, says the bassist, Douglas McCombs: “In the early 1980s, Chicago had an art-school punk-rock scene and an intense jazz community, which in the 1990s somehow coalesced. Now both exist together, in the same venues, on the same stages, even within the same group.”

Tortoise’s steady ascent has opened gateways for fans into areas more interesting than the indie-rock scene that originally harboured the band. Their family tree leads listeners back to the minimalist post-punks Slint, Bastro and Gastr Del Sol, and the psychedelic garage-rock of Eleventh Dream Day, while band members moonlight in numerous jazz outfits, including Isotope 217 and Chicago Underground Orchestra. Tortoise’s choice of guests seemed determined to drag their fans kicking and screaming into a wider frame of reference. For the most part it worked, despite the fact that the festival’s apparent demographic incomprehensibility had, according to the festival’s PR company, scared away potential sponsors.

While US Maple’s confrontational combination of 1970s rock sneer and unpredictable free-music ethics was a twin guitar solo too far for some, for the most part the audience rose to the occasion. To see a rapturous reception for the 71-year-old guitarist Derek Bailey’s disorientating interaction with the Tortoise sound engineer Casey Rice’s samples, to sense the crowd warm to the reinvigorated 1960s saxophonist Fred Anderson’s fatherly glances towards the Tortoise guitarist Jeff Parker, shows that an audience given credit for its intelligence, and a bed in a nice chalet, will respond to quality.

ATP’s success was due to the festival’s emergence as a trustworthy brand and the pulling power of Tortoise themselves, who managed to keep 3,000 people almost silent for 90 minutes of demanding instrumental jazz-dub. But it is also indicative of something bigger.

In another ironic appropriation of standard stage patter, Ira Kaplan asked the audience to shout out if they read The Wire or Mojo. Both these publications, The Wire in particular, step outside the tramlines of what radio programmers and music-magazine publishers usually imagine the public want, and both flourished during the music-press cull that saw Select, Melody Maker and Vox humanely destroyed and buried in a Cumbrian sinkhole. Many tickets were booked through the festival’s website, www.alltomorrowsparties. co.uk, while on message boards, younger fans appealed to their elders for information about which Television albums they should swot up on for the show. The success of the weekend is an example of a shift in the way supposedly unmarketable music can be consumed and packaged. It should set alarm bells ringing in rock land, but the festival’s allies are in the oddest places.

Perhaps because of the lack of luxurious hospitality facilities, there were no Radio 1 DJs or television executives present at ATP, but the former South Bank Centre programmer David Sefton was studying the event for its autumn transfer to Los Angeles, where Sonic Youth will oversee a weekend at his new UCLA posting. The neglected international underground is bursting its banks and overflowing into places where experimental rock music has never set foot before. Like Los Angeles’s most prestigious arts venue. And a Pontin’s holiday camp in Camber Sands on a wet weekend in April.

Television played last on Sunday night, and though bar chatter finally overwhelmed a PA that couldn’t cover the cavernous ballroom,their furtive grimaces couldn’t disguise their enjoyment of their unexpected reunion. As recently as last month, Douglas McCombs didn’t quite believe that the band would show. “Richard Lloyd is holding his cards close to his chest,” he confessed. “He and Tom Verlaine don’t exactly have the best relationship today.” But as Television took to the stage, their craggy faces a Mount Rushmore monument of mid-1970s

New York art-rock, All Tomorrow’s Parties proved itself capable of little miracles.