As metal’s need for speed and extremity reached a fever pitch in the mid-'80s, a band from Flint, Michigan, broke a crucial sound barrier. In their desire to out-Slayer Slayer, Repulsion cranked up the violence, tempo and intensity of thrash while forsaking technical wizardry in favour of brutal punk efficiency. Recorded in ’86, their demo (later released as the album Horrified) made a massive impact on the underground tape-trading circuit—especially in the UK, where bands like Napalm Death, Carcass and Extreme Noise Terror honed the form with crusty punk politics, gorier lyrics and the increased use of lightning-fast blast beats. In the '90s, grind’s palette was enhanced further by bands playing even faster (Discordance Axis), writing songs in Spanish (Brujeria) and adding a refined—if harrowing—literary sensibility (Pig Destroyer). And it’s in no danger of extinction, with more recent adherents like Wormrot, Full of Hell and Nails leading the charge.