"John Larkin" by John Larkin only has two copies in existence, one by his widow and the other by an unknown person. If that name seems unfamiliar, it's because he later became more famous as Scatman John.
It was recorded in 1986 but due to current US copyright law, it won't enter public domain until December 3, 2069.
There's a few copies floating around on YouTube and a FLAC version as a torrent. Pirates are keeping his legacy as a jazz performer alive.