Possible Clues:

• Old pianist with cry of pain leaving Jack Sprat's wife?
• Jazz pianist's arrangement of Waterfalls
• Composer/pianist making his first jazz recordings in 1922
• American jazz musician, d. 1943
• American jazz pianist
• Jazz musician composed Waterfalls
• Musician, learner with hesitation, was flat unfortunately to begin with
• Waterfall's fantastic - he waxed lyrical
• He had a hit with 'The Joint Is Jumpin''
• Jazzman, unlike Jack Sprat, kicking out old wife