Here's a helpful passage from Natalie J. Purcell's Death Metal Music: The Passion and Politics of a Subculture, published by the very respectable McFarland ():
Across the sea, in the UK, Napalm Death would release Scum in 1987. The two-sided album was extremely influential. Though side one featured very punk-influenced guitaring, the second side displayed the impressive Death Metal guitarwork of Bill Steer, which would spur the Grindcore movement. The tempos of the album were incredibly fast, with quadruple-time beats and extremely short songs. The album also featured deep grunted vocals advocating leftist politics. Napalm Death followed Scum with the equally extreme 1988 release From Enslavement to Obliteration. Soon, British Grindcore bands like Unseen Terror, Ripcord, Heresy, Concrete Sox, Carcass, The Electro-Hippies, and others began popping up.... Carcass "adapted the Grindcore formula to include more metallic, chugging sections."
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