I stumbled on this a while back when I was big on reading mp3 blogs. In the few years since I regularly trawled those sites for the mysterious and bizarre gems they posted, many of the really sought-after pieces have been reissued.
For the “Rock In Opposition (R.I.O.)” bands of the 70s, King Crimson was just too simple and pop-oriented. R.I.O. were progressive rock bands from England and Europe who packed so much complexity into their music that the standard prog fans wouldn’t touch them. Their audience consisted of avant weirdos, industrial heads, and fans of more experimental stuff, and their membership was as varied as Henry Cow and This Heat.
Belgian chamber rock band Univers Zero were one of the most intense R.I.O. groups, and Heresie is the best and darkest of their work. It’s sonically dissonant and very, very oppressive sounding in both its density of notes and darkness of mood. Perfect lights-off, scare-yourself music.