Jurgen Goering said: " ... According to them, Gershwin originally
composed this piece for two pianos."

I'm not in a position to challenge this statement, but every time the
BBC broadcasts a version of Rhapsody in Blue -- yesterday it was the
Michael Tilson Thomas, Columbia Jazz Band and doctored Duo-Art roll one
-- it is stated that the first version was for solo piano, with the
two-piano version following, and Ferde Grofe's version following that.

Dan Wilson