Jealous is an understatement. Pretty much every member of Rolo Tomassi is younger, hotter, and more talented than your correspondent – vocalist/keyboardist James Spence recounts how, the last time they played The Flapper, all but two members were under 18, and left in the parking-lot. This time around, he and co-vocalist (and sister) Eva – all < 5 foot of her – hurl themselves around the stage with a vigour that makes your correspondent’s bones ache – although Eva later complains of feeling “a bit poorly”. They’ve evinced such speed – closer to the post-human ruthlessness of jungle and gabba than anything as tame as rock music – since their self-titled debut EP from 2006, through 2008’s Hysterics, and, on tonight’s evidence, their soon-come second album, recorded with Diplo, and the bodies in the venue’s long, low squash can’t get enough of it. The darkened stage explodes into light with ‘Fofteen’s polymorphic crash, the band ricocheting between off-beat rages of metal guitar and second-long passages of jazz noodling, ending on a treadmill of traded screams between Eva and James. The band are, in effect, a collective musical supercomputer, feeding everything and anything through extreme processes of number-crunching – each of their songs contains compressed the dynamic shifts of most bands’ entire catalogues. Hardcore’s overdriven rage is splintered by the fractal-complex brutality of Dillinger Escape Plan and the radio-dial twist-switches of Naked City. The light-show is only one part of the Sheffield band’s increasing professionalism and control, every song a consummate demonstration of violent virtuosity in their collective swerves of direction. As they hit the convulsive mathcore maelstroms of ‘Abraxas’ and ‘Jealous Bones’, a pit’s already forming, the air close with sweat. ‘Nine’ stretches out, unpredictable from one moment to the next – one second a hailstorm of mic-eating screams and relentless pounding, the next a becalmed piano interlude. Material from the new record crops up, alluring in its strangeness: ‘French Motel’ is a stop-start assault going from jagged riffs to dramatic pause to a final 30 seconds of startling sonic violence, Eva thrashing and swaying at every move. They blend perfectly with the earlier likes of ‘Scabs’ and ‘Film Noir’, hardcore pushed so far beyond the template it enters the realms of the avant-garde. By the time they encore with the car-crash bubblegum of ‘I Love Turbulence’, everyone’s shaken, nerves straining for more. We want to know what it is to be sundered. This is how we learn to breathe.