A short video showing some of the loudspeakers used in the nowadays Acousmonium of the GRM:
Again a piece, which can hardly be documented by a video, since it uses loudspeakers underneath the piano and loudspeakers in the concert hall.
…..sofferte onde serene… (1976) by Luigi Nono:
and part II:
Sketches and pictures of focused loudspeakers (1977) by Composers Inside Electronics can be found on their website.