The liner notes to the box set 'Sunday at Village Vanguard' where your set comes from (or maybe you mean "Waltz for Debby") goes into detail how the trio was recorded that day. The kicker is that it was done by a total amateur student. He knew nothing about recording, and it turns out he captured incredible sound. I'm also a huge fan of this set of recordings. May be the best sounding live stuff I've ever heard.