Apart from his work as impressario of the Jazz At The Philharmonic Concerts, Norman Granz developed a carreer as record producer. In 1947 he founded the Clef label, which became a subdivision of Mercury Records but Granz kept ownership of the master tapes. End of 1953 he started a project to record 120 solo’s played by Art Tatum. Tatum was a formidable pianist who was praised for his unprecedented technique and brilliant creativity in terms of harmonies and cord changes. Oscar Peterson is believed to have said about him “he scares me to death”. In the first session an astonishing sixtynine tunes were recorded in four hours, all in one take, except one. In 1955 the recordings were issued as fourteen single albums of three boxed sets titled “The Genius of Art Tatum“ and later reissued as “The Art Tatum Solo Masterpieces”.
Source: Hershorn, Ted – Norman Granz – The Man Who Used Jazz for Justice – Univerity of California Press 2011 – ISBN 978-0-520-26782-4