The two stars were invited by former U.S. President John F. Kennedy to perform for the White House summer interns but the amount of people interested in attending the August, 1962 gig prompted organisers to move the concert from the White House to an open-air theatre by the Washington Monument.
The artists each performed with their bands before teaming up for an impromptu finale and the show was taped by their label bosses at Sony Music subsidiary Columbia Records and stashed away for safe-keeping.
However, only one version of their duet of The Old Black Magic was featured on subsequent compilation albums and the rest of the audio recording was presumed lost for years - until it was rediscovered in a vault shortly after Brubeck's death in December (12).
The tracks have now been released as Bennett/Brubeck: The White House Sessions, Live 1962, and The Lady Is a Tramp hitmaker cannot believe the tape was found.
He tells the Associated Press, "I was shocked they even had it."
Recalling the live collaboration, the first time Bennett had played with his labelmate Brubeck, he says, "It was very spontaneous - a real jam session, where you really don't plan what you're going to sing or how you're going to play it. I just gave Dave the key and the song, and we just went for it. The audience went crazy, and you can hear the reaction on the record."