While the term Grindcore has often been used somewhat interchangeably with death metal, the two started out as very different, albeit similarly extreme, forms of music, despite becoming more alike over the years. When it first appeared in the mid-'80s, grindcore in its purest form consisted of short, apocalyptic blasts of noise played on standard heavy metal instrumentation (distorted guitar, bass, drums). Although grindcore wasn't just randomly improvised, it certainly didn't follow conventional structure, either; while riffs could sometimes be picked out, pure grindcore never featured verses, choruses, or even melodies. Grindcore vocals sounded torturous, ranging from high-pitched shrieks to low, throat-shredding growls and barks; although the lyrics were usually quite verbose, they were very rarely intelligible. Grindcore's jaw-dropping aggression was so over the top that pointing to its roots in thrash metal and hardcore punk hardly gives an idea of what it actually sounds like. Indisputably, the band that invented grindcore was Napalm Death, whose 1987 debut album Scum is also perhaps the most representative example of the style. In Napalm Death's hands, grindcore was actually rather arty, a sonic metaphor for the bleakness, violence, and decay of modern society; the group's lyrics were additionally packed with angry social commentary. More extreme in the lyrical department was Carcass, the only other band to really epitomize the original grindcore sound; their gruesome, gory rants were literally taken from anatomical textbooks for maximum shock (and gonzo comedy) factor. However, grindcore's original form was inherently limiting, and its intensity could easily turn into self-parody; on Napalm Death's second album, they had already begun to experiment with industrial textures, a fusion that would prove popular not only with bands who loved the jackhammer rhythms a drum machine could provide, but also with slower, moodier bands like Godflesh (itself a Napalm Death offshoot). Grindcore's blistering intensity was assimilated not only into underground heavy metal, but also into avant-garde and experimental music circles; Japanese noise bands like the Boredoms and Merzbow found it inspiring, and jazz musician John Zorn formed the grindcore-inspired group Painkiller (which featured former Napalm Death drummer Mick Harris). Although pure grindcore was a distinctly British phenomenon, the early albums by the Florida band Death -- which ratcheted up the aggression and morbidity of prime Slayer -- had a raw, crude, assaultive quality that made them extremely similar. Apart from adopting the low, demonic growl of the grindcore vocal style almost wholesale, American death metal bands with relatively limited technical ability who played at fast tempos often resembled grindcore outfits with song structures. In fact, by the '90s, Napalm Death's sound was virtually impossible to separate from either death metal or grindcore, and Carcass had become a full-fledged, even melodic, death metal band. One of the very few bands to stick with grindcore's original form was A.C. (aka Anal Cunt), which primarily employed it to a snottily humorous effect.