Computer music has a long history and I'm not sure what exactly you mean by "radical/extreme", as a lot of early computer music could well be defined that way due to it being unique for the time. There's also the fact that a lot of new material is somehow digitally generated, recorded or produced. The computer is just as standard an instrument as anything else now.
I've always liked
Barry Truax. Main deep, slow moving drone pieces digitally generated by early computer systems, occasionally complimented by acoustic instruments or voice. The tone poem "The Blind Man" has an eerie, moving quality about it.