While Saxtet was playing pre-concert music in the foyer of the London National Theatre some years ago, a suave, portly gentleman approached us and said, "Keep up the good work boys". Because he was clearly from the USA, I asked " how about an American in Paris?" and he responded "What's wrong with an American in London?" We immediately launched into this arrangement. That gentleman was the late Leonard Bernstein.
This arrangement has been authorized by Warner/Chappell and is a condensed version of the original, as is the arrangement of Rhapsody in Blue.