In 1940 [record executive Edward] Wallerstein, who was now at Columbia Records, signed me up again. The first recording I made there was “Clair de Lune,” and it had a special role I never knew about until many years after World War II. Wallerstein, who was with the wartime Office of Strategic Services, told me that “Clair de Lune” disks had been used to send messages to American prisoners of war. The device was simple and played on the fact that the quality of recordings in those days was not all it should have been: a Morse code message would be scratched onto a disk, which would then be sent to a Red Cross station, where it was played on the air. The prisoners would know it contained a coded message and listen for it, but to anyone else it seemed like just another record with bad surface noise.
—Andre Kostelanetz (in collaboration with Gloria Hammond),
Echoes: Memoirs of Andre Kostelanetz, 1981