The composer Burton Lane describes George Gershwin’s playing:
You could feel the electricity going through the room when he played. He could transpose into any key with the greatest of ease. He had total command of what he was doing. Musical surprises, unusual changes of keys. He was one of the few composers who had a real sense of humor.
Cited in: Greenberg, Rodney (2008) George Gershwin. New York: Phaidon Press, p.47.