The theatre director Rouben Mamoulian describes Gershwin’s playing:
George at the piano was George happy … like a sorcerer celebrating his Sabbath. He would draw out a lovely melody like a golden thread, then juggle it, twist it and toss it around mischievously, weave it into unexpected intricate patterns, and hurl it into a cascade of ever-changing rhythms and counterpoints.
Cited in: Greenberg, Rodney (2008) George Gershwin. New York: Phaidon Press, p.47.