I used to do this a lot in high school. For a second I thought it was one of our tapes!

My friends who play this sort of thing nowadays (all of whom are both very technically proficient and musically educated players of jazz) call it, I believe, "improvised music." It owes an obvious debt to jazz, but I think they prefer not to bring any baggage that comes with that word.

It's fun to hear live, as the musicians switch instruments and explore their environment, sometimes doing a spacial thing with the sound.