Nowadays, these techniques and tools are far more prevalent in improvised music and I think (rather ironically) many standout improvisors actually use the most rudimentary equipment possible. Toshimaru Nakamura performs on what he calls a 'no-input mixing board'. Quite literally, he takes a small portable mixing deck and wires it to itself, creating feedback which he then manipulates with effects boxes and the simplest tools available: the board's volume, pitch and pan controls. Through singular dedication to this simple tool, he's become an adept, responsive and expressive collaborator.
Dusted Machinery is a recent album finding him in a duo with a European impov titan, John Butcher. Butcher's astounding store of extended techniques, keeps him closely tethered to Nakamura's squeals and rumbles. The delineation between organic and artificial frequently eludes you here.
There is very little more Earthbound than the saxophone. It's been said that—through some mystic combination of the breath, reed, echoing chambers and complex fingerings—the saxophone has the most human expression of any classical instrument. It's why there's more famous jazz saxophonists than any other instrument. Conversely, keyboards and electronics struggle to this day to be fully accepted as valid improvising tools. (The 70s dalliances of fusion jazz didn't help the case.) It's a base-level challenge to create a truly unique voice on a keyboard. Interestingly, even if they have the world of pitch and sound at their fingertips, that may also be a detriment. Limitations can be an amazing wellspring of creativity. If your instrument can make any sound imaginable in any pitch from subsonic to dog-whistle, you may well have too much leeway to operate, artistically.
The exploration of unknown possiblities crossed with restraint are the fundamental elements of these records. With no written material, each duo must quickly define the parameters they are going to work withing to get down to the real business of improvisation: communication. Listening to this most unlikely combination of instruments as they find a shared language is a revelatory window into the very art of the music itself.