There are three activities that rural Oxfordshire excels in: voting Tory, playing Aunt Sally, and running tiny music festivals. Alongside Truck and Cornbury, on any given summer weekend you can find a strange little festival somewhere in the county, with friendly musicians playing to small gaggles of happy listeners. About half of them are run by Phil Garvey, seemingly. However, even in this environment, Tinderbox stands out as an oddity. In what is essentially someone’s garden just outside Cropredy, a small clutch of customers could listen to some experimental, primarily improvised music, sup a pint or a cuppa and eat a burger. And that’s it. Nobody selling funny hats, nobody trying to tell you about the social situation in Borneo, no hastily concocted extreme sports, just a gazebo with some leftfield music, and a few dozen ears to give it a chance. And, at least one pair of ears can confirm that the quality was incredibly high.

Ostrichbox, a trio of composition students from Birmingham, open the day with three laptops and some glitchy, post-IDM rhythms. Much of the set consists of pretty but inessential sonic baubles, all metallophone ostinati and tinkling bells, but there are moments of bleak beauty when a forlorn vocal enters, and melacholy melodies play against the chirrups and hums.

This ghostly folk song technique is built upon by Southend’s Lost Harbours, who wrap guitar, flute and primarily wordless vocals in a wraithlike mist of reverb and delay. If you want the soundtracks to Once Upon A Time In The West, Twin Peaks and The Wicker Man distilled and served chilled, this excellent act should fit the bill.

In the US, the history of free and improvised music seems to be closely allied to revolutionary and race politics. Here in the UK, it always seemed closer to light socialism, gardening and theatrical pranksterism. Bolide bear this out, a clattering Art Ensemble of Brighton blowing hell for leather, but more interested in making each other chuckle than spreading a message. The set is a squalling, ersatz space ritual, but despite the presence of myriad reed instruments, a gong and some fetching kaftans, this isn’t one of Can’s ethnological forgeries, it’s more like musicological fuckery. Jon Hassell’s Fourth World technique involved taking global folk musics and immersing them in expensive Western gloss, but bands like Bolide offer a Fifth World, in which elements from across the planet sound equally cheap when smeared together in one long faux-freak blast. It’s a more realistic vision of international cultural exchange, and it sounds a damn sight more entertaining, too.

Temperatures, from London, are another highlight, pitching drums and bass against vintage electronic hums sourced form a large analogue rack that may or may not be in tip-top condition. Certainly, the electronic pulses have the wayward quality of an awkward child, and much of the fun of the set is the pull between tight rhythms and sloppy sonics. The bass especially sounds as if it could morph into a self-conscious school swot jazz funk at any moment, whereas the vocals are tiny distorted guttural fragments, the logical conclusion of Alan Vega’s bargain Elvis schtick. An act that creates lots of intrigue from minimal materials.

It seems harsh to give the worst review to the act that has travelled the furthest to perform to such a small crowd, but Sylvia Kastel and Ninni Morgia from Italy – seriously – have the least to offer, in their mixture of cave-drip guitar and wailed ululations embellished by vocal treatments and guitar pedals. There are enjoyable moments, the odd Fred Frith guitar flurry, or a ring modulated swoop, but the set feels like a parade of effects rather than a musical event. Hell of a lot of ear-drilling treble, too, for a chilly afternoon.

We’ve seen festival organisers Red Square a couple of times, but today’s set is the most satisfying, perhaps because they’re playing on home turf (literally), rather than at the bottom of a Friday night rock lineup. Their new drummer plays more straightforward rhythms than his predecessor, but these actually work wonderfully, providing a solid backdrop for simmering free guitar and some lightly ‘traneish sax lines that disappear into a labyrinth of digital effects. They’re the band who pitch their improvisation closest to rock dynamics, Ian Staples’ compressed guitar sound owing far more to Hendrix or metal shredders than to Derek Bailey. They occasionally get bogged down in a rhythmic furrow, and a the odd tempo switch wouldn’t hurt, but the final track is a surprisingly groovy number, bridging the gap between Maceo Parker and Evan Parker, so this is a small criticism. Ian, however, is wearing a deep red outfit and sky blues shoes; oh dear, bring back the kaftans.

Shatner’s Bassoon are a five-piece from Leeds, and are easily the most technically minded of today’s acts. They have plenty of all-out free passages, but also some tightly arranged heads and traditional jazz solo spaces. There’s a Hancockesque Rhodes sound ladled liberally, and some nods towards supper jazz, reggae and even calypso in the maximalist compositions, proving that sense of humour is as high on their list as a sense of exploration. After a day of music that tended to clamour or drift, it’s refreshing to see a rhythm section signalling complex breaks, and a traditional sense of structural dynamics. Shatner’s Bassoon are funny without being silly and musically intricate without being introspective. Chris Morris would be proud.

Funnily enough, festival closers Space F!ght, from York, sound as though they could have been used by Morris in the background to an episode of Jam. They place textural guitar and sax over crisp, Black Dog style beats, to create an avant-comedown music of jazz fragments and deep sonic horizons. In a way their set might have worked better after a long day of sunshine and energy, rather than an afternoon of huddling away from the rain, but they still create a diverting sound world.

And as we walk all of ten yards back to the car, Tinderbox makes us think of The Streets’ lyric, “You say that everything sounds the same/Then you go buy them”. Anyone who’s moaned about the corporatisation of music festivals and predictable lineups, whilst being strip-searched in the queue for their five pound can of Tuborg, should check out next year’s Tinderbox: you might discover some of the best music you’ve ever heard, or you might hate every second of it, but you’ll know you’ve seen something created with love and honesty… and you might even get a free cup of tea if you ask the lady behind the counter about her herb garden.