This is probably (although I can't swear to it) the only recording in existence of a concert given by the Marian McPartland Trio at St. Anselm College, on November 1956.
The tapes have been sitting on a shelf in the archive for years and they are a mess. They appear to have been recorded by a student who was also in charge of the PA system (just a hunch). It's one microphone and it distorts from time to time, especially during crescendos. The tapes are brittle and splices pop every twenty or so feet. The tape wasn't erased properly so there were bits of sermons and cooking shows to contend with and a choir managed to bleed briefly through on one song which I managed to isolate on another pass using the old "hold thumb at strange angle to playback head" method.
The description sounds worse than the actual hearing. And even though it is far from perfect, it's a great concert by a trio who individually are legends in Jazz and collectively offer a seamless reason why.
A little less than an hour and only the introduction is missing from the tape and the first ten or so seconds of the first song. Otherwise, it's the whole concert. Never released, never broadcast - probably never knew existed.