When Lennie Tristano died in 1978 none of his many amazing recordings were available. They were all out of print. Unbelievable! Thankfully there are many reissues around today and I'm sure with more to come. You can get all the 1946 trio recordings on The Complete Lennie Tristano on Keynote
and the 1947 trio on the Rarest Trio/Quartet
(1946-1947). I also recommend his recordings Live in Toronto
as well as Live at Birdland
(1949). Atlantic has now made available his Complete Atlantic Recordings
from the 50's (or you can buy many of them separately). And don't forget Intuition on Capital with the first recording of free jazz. There are also quite a few more available which I haven't heard yet but I'm sure are equally great. If you haven't checked out much Lennie Tristano yet, go get busy!