To the Vortex at midnight. Considering it’s still only May, I’ve seen some pretty remarkable gigs this year: Portishead, Vampire Weekend and the mighty Raconteurs last week; Peter Walker’s flamenco/raga masterclass; Neil Young soloing endlessly into the full glare of a Klieg light, and so on.

To the Vortex at midnight. Considering it’s still only May, I’ve seen some pretty remarkable gigs this year: Portishead, Vampire Weekend and the mighty Raconteurs last week; Peter Walker’s flamenco/raga masterclass; Neil Young soloing endlessly into the full glare of a Klieg light, and so on.

Last night, though, was one of the best yet. The Necks, as I’ve mentioned before, are a piano/double bass/drums trio from Australia. Apparently, their music is completely improvised: they arrive onstage, start playing, and work their way to some kind of conclusion about an hour later. Here, they’re playing the Vortex jazz club in Dalston. One show, in the evening, features two sets, and was sold out ages ago. This one begins at midnight, and features just one traditionally elongated, utterly absorbing piece.

It begins, not atypically, with a genteel, romantic solo flurry from the pianist, Chris Abrahams, a player who hovers delicately somewhere between, very roughly, Alice Coltrane and Steve Reich. Gradually – well, comparatively rapidly by their measured standards – the Necks pick up speed and intensity. Tony Buck has a cosmic cluster of bells out of sight behind his drumkit, and is meticulously working at his snare with a scrubbing brush. Lloyd Swanton stands with his eyes closed, seemingly meditating on every nuance of the music, waiting to make his discreet entry. When he does, he sways along with his double bass, holding it like a sailor clinging to the mast in a storm.

Soon – after maybe ten minutes, though I’m not looking at my watch to verify –the music has become full and intense, with great pointillist clusters of piano notes and a relentless flutter of cymbal and snare and bells which remind me of the Boredoms circa “Seadrum”. My sketchy knowledge of jazz means the rock references come easier to me, so there’s something of Can here, too, and Swanton’s frantic bowing at his bass adds a thickness that’s oddly reminiscent of Sonic Youth, something like “Cross The Breeze”, perhaps.

What they create here – without ever looking at each other, weirdly – isn’t something spacious and near-ambient like “Townsville” or “Mosquito”, but instead a kind of sombre rapture. It’s extraordinary, and so compelling that I find myself, a gauche non-musician, wondering how the hell they do it. Do they use rehearsed themes as a springboard? Do they try and surprise each other – I suspect not, since unlike some other free music, what the Necks do is distinctly harmonious rather than competitive.

And how does this piece – a relatively pithy 45 minutes, it turns out – fit in with the two they played earlier? One of the many joys of The Necks is learning their minute, exquisite variations, while not being entirely aware of the full picture. What is the full extent of their range? How do they evolve and fluctuate? And how tired must they be at the end of the evening?

Walking to the bus stop, a fox crosses my path and walks slowly across Kingsland Road, stops, looks, cocks its leg against a lamp-post, and pads elegantly down Sandringham Road. I wonder if it does that every night, two or three times, too?