musique concrete was basically just a term for music made with 'fixed sounds' (tape) as opposed to music made by / composed for instruments. it was sort of invented by the paris composers of the GRM. Other (french) studios or 'schools' named it acousmatic music, which is basically 'music for speakers'. so in the true meaning of the term one could of course use it for almost all electronic / tape-music / even noise, but that wouldn't make sense really. the terms gets thrown around quite randomly nowadays for all kind of tape/collage music, but it has nothing to do with this really. back then it was also used for studio compositions with recorded instrumental music.
i never understood the hate for 'academic' avantgarde music, that the word is often used as an insult around here (and elsewhere in the 'underground scene'). the academia / university studios were just the only ones back then who had the fundings and interest in electronic equipment and radical sonic experiments. before that it was all chamber music at rich people's homes or orchestras at concert halls. most of those 'academic' people and 'art fags' where in fact more 'punk' and subversive than most nowadays noise people. even if it was happening at (mostly) well-funded studios the work was actually sub-cultural and public presentations caused quite some trouble in the early days.