“The project began when Kubrick encountered a book in 1985, Swing Under the Nazis, written by another jazz enthusiast, Mike Zwerin, who left music for journalism and spent years collecting stories of jazz preservationists in Germany and formerly occupied Europe. One of those stories—of Nazi officer Dietrich Schulz-Koehn—struck Kubrick as Strangelove-ian and noir-ish. Schulz-Koehn published an illegal underground newsletter reporting back from various jazz scenes in Europe under the pen name, “Dr. Jazz,” the title Kubrick chose for the film project.”
(Source: openculture.com)