Attempting to come to terms with Fats Waller's recorded output can seem a daunting task at first because he was so extraordinarily prolific. The history of his recording sessions spans his entire professional career, from the time he was 18 years old (when he cut his first discs, in October 1922, a session at which he recorded two piano solos) to his final session on September 23, 1943, less than three months before his death. During these twenty-one years of activity as a professional musician—when he made hundreds of live appearances in shows, clubs, on tour, and on radio—he made over 600 sides, in almost every conceivable format: on piano rolls; as accompanist for singers; as soloist on a variety of keyboard instruments, including piano, pipe organ, electric organ, and even celeste; as a sideman under leaders like Fletcher Henderson, Jack Teagarden, and Ted Lewis; as a sideman with small groups (Morris's Hot Babies and McKinney's Cotton Pickers); as a leader of his own small ensembles ("Fats Waller and His Buddies," "Fats Waller and His Rhythm," "Fats Waller and His Continental Rhythm"); on transcription discs designed for broadcast on radio; as a singer in each of those formats; and even on one occasion as one of a team of duo pianists (with Bennie Paine).

Any scheme that attempts to classify this vast body of recorded material, then, needs to take into account both the category of performance and the chronology of Waller's recording sessions. This chronology can be roughly (and somewhat arbitrarily) divided into five periods or groups: October 1922-November 1926 (a kind of apprenticeship for Waller; these