I finished up listening through in the last month the complete collection of Peter Kowald Duos, from the FMP label, which you can purchase VERY cheaply from Destination Out right here. Peter Kowald was a German free improv bassist who played with everyone in the scene: Bill Dixon, Peter Brotzmann, Joe McPhee, Abbey Lincoln, Wadada Leo Smith, The Globe Unity Orchestra, Karl Berger, Julius Hemphill, Evan Parker, Derek Bailey, Joelle Leandre, William Parker and many more (which you hear some of these in the duos)!
He unfortunately died of a heart attack in 2002, but in his 58 years on this planet gave us a lot of incredible recordings and sounds, while helping spearhead many tours and festivals, getting this freer musics out there to the world. His goal was to create international ensembles of musicians from all over, to create extraordinary musics (which some of the larger ensembles he was in could achieve). He had a huge amount of technique, a a big ear for musicality, and a bag of extended technique that gave him access to sounds most bass players have never heard of (unless maybe you're Joelle Leandre or William Parker). I can't emphasize enough about how beautiful this musician was, giving his all and more for the music. There is a documentary on that scene I watched a while ago (blanking on the name of it), where it shows he would sometimes tour in europe on a bicycle, with bass on his back and everything, ready to go.