L’improvisation musicale au 20ème siècle (PDF) is a mémoire I’ve written ten years ago about the evolution of improvisational practices in contemporary music, during my studies of aesthetics in ULB (Brussels). It was directed by Thierry Lenain. With all its flaws, I guess it can be of some interest here.
Also, it includes an interview of the great band Pelt, with Mike Gangloff, Patrick Best, Mikel Dimmick and Jack Rose, after a show in Brussels that same year. For a more recent one here.