Robbie and I lightly butted heads on this a few months ago, but
I'll say it again:  Gershwin was not an orchestral arranger, he was
a gifted pianist who wrote stuff that other people puffed up into
sometimes bloated versions of what were essentially tuneful and
distinctive improvisations.

Just because he had such magnificent chops on the keyboard didn't
mean he could automatically orchestrate, which is an art in itself.
And since "Rhapsody in Blue" is his baby, he gets to play it at
any tempo he wants.  ;-p

Claudine Jones
San Francisco