By the campsite, teams of people roll around playing zorb-ball inside inflatable spheres. Onsite, dancers that look like Tim Burton toybox marionettes jerk out stilted moves on a stage set midway between a high art museum and a towering neon phallus-like sculpture. The mascot is a cow on stilts. It’s fair to say that Poland’s Open’er festival – which takes place on the site of Kosakowo Airport – is a surrealist’s wonderland, even before R&B legend D’Angelo comes on dressed like a Noel Fielding impersonation of a funky ‘70s Harlem pimp.

But the strangest sight of the four-day shindig, in this writer’s eyes, is the former busker who’s been Cinderella’d to stardom as A$AP Rocky’s very own Dido. “Ladies and gentlemen, Joe Fox!” the New York rapper bellows, introducing a singer whose most high-profile shows, until A$AP discovered him busking in Soho at 4am and snaffled him to write sumptuous hooks on his ‘At.Long.Last.A$AP’ album, had included regular slots at this writer’s Camden clubnight. Sure enough, Joe adorns the likes of ‘Holy Ghost’ and ‘Jukebox Joints’ with a melodic soul, sophistication and authenticity, while A$AP’s inventions in narcotic psych rap (‘L$D’, thes gorgeous ‘Excuse Me’) make us feel trapped in the belly of a very stoned Kraken the sea monster.

The Vaccines doing their thing.

Open’er loves its outsiders – its disco freaks, busking bums, cultural high-thinkers and pretend priests. On Wednesday, as Drake impregnates half of Poland with his ‘sensitive’ superhuman-sperm-count loverman rap on the main stage, Father John Misty (not a real clergyman, get the last rites from this guy and you’ll be pitchforked in the jacksy for eternity) rains scorching space-gospel fire and brimstone onto the Alter Tent. At 1am, South African ravers Die Antwoord bound about in outfits resembling a Klu Klux Klan graffiti wing, sounding like Bowie’s ‘The Laughing Gnome’ has grown up and got into gabba techno.

The “best audience of the entire tour” (copyright every act all week) have a tendency to mistake this hornet-infested airstrip for Pacha at dawn. Come Thursday, Major Lazer draw one of the weekend’s biggest crowds to their wild-ass Ibiza foam party rammed with ticker tape cannons and dancers doing the splits to samples of ‘I Like To Move It’. And The Prodigy’s monstrous techno assault owns Friday; Keith Flint the ultimate robo-Lydon and Maxim leading “all my Polish people!” in ‘Breathe’, ‘Voodoo People’ and the Duran Duran-on-a-Magaluf-stag ‘Omen’.

The Libertines in action.

Tiring of dumb dance thrills? Then embrace Open’er’s cerebral side. In the Tent Stage on Friday Jonny Greenwood recruits the London Contemporary Orchestra to perform his experimental modern classical pieces.This generally involves the Radiohead guitarist fondling a sitar or piano while the LCO try to saw their instruments in half with their bows. At its calmest ‘Application 45 Version 1’ resembles Snow White in a k hole, and at its wildest ’88: Sketch’ is essentially a woman punching a piano keyboard like she’s just lost it in a bitter divorce. Baffled? Just wait until St Vincent performs prostrate on a hospital couch, repeatedly mimes cutting her own throat and has what appear to be very melodic stomach cramps during her enthralling Saturday show.

Open’er appreciates the finer arts so much that Alt-J’s wispy monktronica is greeted with such roars you’d think One Direction had just arrived, but it’s a bumper year for rock geezers too. Eagles Of Death Metal spew trucker boogie sex rock for an audience of “hungry cannibals of rock’n’roll” while pretending that singer and part-time nipple Jesse Hughes has married lost-on-his-way-to-a-ZZ Top-rehearsal guitarist Dave Catching. The Vaccines’ incredible barrage of retooled golden era rock’n’roll leaves the field pitted with steaming pop craters and Thursday headliners The Libertines far upstage their surprise Glastonbury appearance with a wild and righteous rampage through their wasted youth anthems and ballroom blitzes. “The Libertines are back at their best!” Pete yowls, plonking a fan’s sailor hat on John Hassall after a moving ‘You’re My Waterloo’ full of classic Doherty references to Judy Garland and Tony Hancock. Agreed.

Mumford & Sons drew one of the biggest crowds of the weekend.

The week really belongs to Kasabian though, tackling the final night with the cocksure poise of a band admiring the cut of their new headliner robes. They strike like a meteorite, scattering chunks of molten rock majesty: the Diplodocus stampede of ‘Bumblebeee’, the wobbly space ABBA of ‘Eez-Eh’ and the way ‘Days Are Forgotten’ rides in on a black gothic-western horse. Before long Serge is dancing down the barrier walkways like a rubber-limbed disco king, they’re dropping wink-wink snippets of The Doors’ ‘People Are Strange’ and Fatboy Slim’s ‘Praise You’ and invading Disclosure’s fest-closing set, the embodiment of Open’er. Innovate hard, and don’t stop the dance.

Kasabian being boisterous as ever.