Autechre perform in complete darkness. ‘Do not move unnecessarily’ is the written instruction, a droll imperative twenty years into a career begun in dance music and probably sensible advice to a sold-out crowd of ageing ravers wrapped for bitingly cold weather.

First though, making full use of the strobes, Russell Haswell rattles through a set of cathartic noise. He starts as he means to go on with some mercilessly tortured no-input feedback, as if inserting a sentient Austin Allegro into a wood chipper. White noise is vigorously scoured, oscillators judder and circuitry howls. He appears to be trying to reduce his modular synthesiser to a pile of blackened smoking cinders. Clowns have taken over the asylum and the world is officially in freefall chaos. Helpfully, Russell Haswell has provided the live soundtrack.

Lights out and without fanfare Autechre begin. The first twenty minutes are dazzlingly wonderful. Ripples of resonating burrs begin to fill the room. Liquid, alien textures twist over mysterious thumps and booms. Periodically a standing wave of purest bass rolls through the crowd, a full-body benediction that makes everyone moan with pleasure. It’s ridiculously cinematic. When War Of The Worlds is remade again, these are the sounds that must accompany enormous cylinders slowly unscrewing, insectile scrabblings and the sinister assemblage of terrible machines. In the darkness we lean forward, eavesdropping upon truly alien transmissions.

Sign up to our daily email to receive

the latest news from across Bristol every morning Your email address

Rob Brown and Sean Booth have described their methodology of coaxing and nudging software patches of generative algorithms as a rudimentary form of artificial intelligence; coded instruction sets as extensions of their personalities. This is knotty, furiously uncompromising music that sometimes collapses into a fidgeting morass of noise, like a man fighting his way out of a balloon, but there are regular flashes of dry northern wit (Exhibit A: Theme For Sudden Roundabout.)

A straightforward thumping house beat is greeted with relieved cheers until it sours, sagging and elongating, dance music in callipers. Later, bracing organ chords blast out, seemingly lifted directly from The Abominable Dr Phibes. To close, the pair assemble a muscular lullaby of Chinese cymbals and choral voices, scraping and clanging, morphing and smearing.

In 1977, the Voyager space probe was launched into deep space containing a golden record etched with Bach, Mozart, Blind Willie Johnson and Chuck Berry. Perhaps in retrospect, launch should have been delayed until it could include a box set by Autechre with the note, ‘Return To Sender’.