Green’s Dictionary of Slang

Rhapsody in Blue n.

[rhy. sl. ult. the musical piece ‘Rhapsody in Blue' composed by George Gershwin in 1924]

a Jew.

(ref. to 1970s) A. Marcuson on Twitter 11 Mar. 🌐 I do remember one of the old time, Sephardic rug dealers saying to me when I mentioned I was Jewish, ‘I didn’t know you were a Rhapsody in Blue!’.