The Necks, Vortex Jazz Club, London

For many years, north-east London's most welcoming bohemian outpost, The Vortex, used to operate from a small upper room in Stoke Newington, before moving to its current location in an even smaller upper room in nearby Dalston. Tonight, the tiny space is packed to the rafters – or rather, to the ceiling's hi-tech exposed girders and air-conditioning conduits. The latter don't seem all that effective against the combined humidity of a roomful of people – in fact, it appears as if most of the patrons have passed out with heat exhaustion, their eyes closed and mouths slightly agape.

But every now and then a hand will raise a bottle, or a head nod rhythmically, subtle proofs of consciousness careful not to puncture the delicate meniscus of sound created by The Necks. Even the band themselves play most of the set with their eyes shut, focusing on the music in order to pick up and develop the minutiae of each others' parts, pianist Chris Abrahams and drummer Tony Buck poised like hovering hawks over their respective instruments while bassist Lloyd Swanton uses his slim, elegant double bass for support as he sways to the rolling waves of sound.

To describe The Necks as an improvising jazz trio is something of a misnomer: improvised jazz so often resembles a battle, each player striving to impress – or, in the classic tradition of "cutting contests", outdo each other in skill, complexity and imagination. But although The Necks have no shortfall in any of these categories, they have managed to subsume their individual ambitions to the collective aim, in a manner which has clearly taken years of interaction to perfect.

Tonight's two sets are typical: the first opens with an unhurried piano motif repeated over a yawning monotone of bowed bass, gradually becoming more florid, like a flurry of snowflakes building into a blizzard – an impression heightened by Buck's sleigh-bells and temple-bells. One could be in a Himalayan monastery, watching the sky turn ever whiter through a frosty susurrus of cymbals, while Swanton conjures a billowing cumulus of bass.

The second set builds up more of a propulsive groove, although the Himalayas are still brought close by the squeak and rattle of Buck's opening percussive figure, which resembles the steady creaking of a Tibetan prayer-wheel. Save for a microphone glitch that sends harsh noise reverberating through a few seconds of the first set, both pieces are mesmeric, luminous delights, exactly the chilled refreshment required to stave off the evening humidity.