This composer's works include "Short Story," a duet for piano and violin, and the one-act opera Blue Monday. After a trip to Havana, he wrote Rumba, which is now known as his Cuban Overture. He also wrote an opera in which Clara sings "Summertime" on Catfish Row. He also composed a Piano Concerto in F, as well as used a taxicab horn in his, "An American in Paris". For 10 points-name this American composer of Porgy and Bess, An American in Paris, and Rhapsody in Blue.