Thematic: According to John Cage, Stefano Scodanibbio was one of the most important contemporary double bassists. He was his favorite. I agree with him. Below is a random example of his music on YouTube. I did not choose it well. My favorite CD of his music played by Hakon Thelin looks like this: (Strong recommendation)
It is in Amazon Music. I listened to the Sequenza and it sounds
great! Scodanibbio has superhuman control of that instrument.
Speaking of double bass, we talked about
Aus den sieben Tagen by Stockhausen earlier. I remember getting a box set of LPs (DG, I think) of it from the music library when I was a student and being largely unconvinced. At the time I was much impressed by
Kontakte,
Mikrophonies,
Hymnen, Mantra etc. and 7 Tagen was boring by comparison, a bit incoherent. The sleeve notes explained it was group improvisation based on poems penned by Stockhausen, although Stockhausen insisted on calling it intuitive music, wanting to distance himself from the word improvisation. (That recording may be of a different version of the composition than the one you mentioned previously because you described a soloist improvising to a tape accompaniment, iirc.) But I do remember from all those years back that I was impressed enough by the double bass player to remember the name: J.F. Jenny-Clark. This name has come up several times in my listening since and he always impresses. There have been some interesting narratives told by participants of those seven days. I should seek them out again.