Noone, anywhere, has a cohesive all-encompassing explanation of the traits that define "Industrial Music". So we're just gonna make shit up.
Although they themselves were influenced by late 1960s experimental/psychedelic, Krautrock and noise-rock bands, most people lay the blame for Industrial Music on the band Throbbing Gristle. This probably stems from the fact that they referred to their music as industrial and started a record label called Industrial Records. Maybe, just sayin'. They were known for their home-built instruments, confrontational shows (including an infamous early stage setup where you had to choose whether to hear or see the band), and tendency to push uncomfortable extremes of both high and low sound frequencies, on top of already controversial lyrics and image. We'd be willing to guess that if they could have pulled it off, they would have showed up on the doorstep of every person who bought one of their albums, just to personally kick them in the balls.
'cause they crunk like dat.
Other early Industrial Music bands, such as fellow British act Cabaret Voltaire, American acts Z'EV and NON, and Australia's SPK were initially similarly confrontational; embracing totalitarian, occult and transgressive imagery, Dadaist/Situationist performance art, references to controversial authors like William S Burroughs, and frequently nihilistic and culturally subversive subject matter. What these seemingly unrelated acts shared is less about musical influence than symbolic influence; or so says that cute chick behind the counter of the sandwich shop with the dreads and facial piercings.
In any case Industrial Music as-such technically ended around the same time first-wave punk did, and in 1980 shattered into a bunch of tedious sub-genres that don't mean dick to pretty much anybody, even the vast majority of people that claim to like Industrial Music. Even the most devoted rivethead (technical term for Industrial Music fan) isn't gonna correct you if you casually refer to Frontline Assembly, Current 93 or Coil as Industrial; and if one does, say they sound like a raver with all their corny sub-genres and shit. Then ask them if Psy-Trance is a subgenre of Industrial. Protect your nuts first tho, they'll probably be wearing steel-toed boots.
Or occasionally something more sensible.
During the rest of the 80s, Industrial Music began to develop more of a rock-based sound as some returned to their post-punk roots, while others rallied around Chicago record label Wax Trax! Records. With a few notable exceptions (Canada's Skinny Puppy and Einstuerzende Neubauten from Germany, for example), Wax Trax! began to define Industrial Music the way most people know it now. Late-80s/early-90s successes by industrial-metal bands like KMFDM, Godflesh, and Ministry paved the way for Trent Reznor, who was desperate to make people forget the flaming piles of synthpop dogshit he was responsible for in the mid-80s.
Reznor led his industrial band Nine Inch Nails to achieve massive commercial success in the early 90s (more than any band in the genre), wait five years, release a dreaded double album, and hide for five more years before re-booting the band with a much less industrial style, because he's
an opportunistic twat, some sort of musical genious or something. One would be inclined to thank God for the the massive mountains of booze and drugs he consumed in the late-90s that prevented him from riding the trend that could have turned him rap-metal.