As with all of Woody Allens comedies and dramas, casting Sweet and Lowdown with the right actors for the alternately funny and tender roles was the priority. Woody Allen says of his ensemble, "I loved working with everyone in the cast and had a great time on the set. I was very proud to work with Sean Penn, who is a brilliant actor. Samantha Morton was a pleasure, Uma Thurman was wonderful and the whole thing was a great experience."
The experience began with Woody Allens life-long love of jazz music. Although jazz themes have wended their way through the background of many of his prior films, Sweet and Lowdown is a Jazz-age fable about an artist who captured both the renegade and bittersweet spirit of jazz. Allen conjured the fictional Emmet Ray from his imagination, but the character resembles a composite sketch of several real-life jazz artists some of whom exhibited sublime virtuosity in their art but chaotic, comical foibles in their personal lives.
To play Emmet Ray, Allen chose Sean Penn whose extraordinary range has allowed him to forge an indelible roster of on-screen characters. Penn, who has never played the guitar, learned the hyper-dexterous fingering for some 30 virtuoso jazz songs. Says Woody Allen: "Sean fulfilled my deepest wishes for the role. It was a real treat to work with him."