He's great. He was one of my inspirations in playing "free" cello (when I was a practicing musician).
I have the original BYG vinyl of Seasons, as well as a Sunspots CD (PM if you would like a burn). The CD is not a needle drop, but from master-tapes, and sounds phenomenal compared to the low-quality BYG vinyl.
There's another one, on French Leo, My Country, that is rare as hen's teeth but extremely rewarding.
I also dig his work with Burton Greene in the Free Form Improvisation Ensemble and with Bill Dixon and Frank Wright. A fantastic player and very influential albeit in a small circle of players/composers.