Sherry and Krall Magic checks in to tell me that he recently heard a "complete clear as a bell interview with Hardeen" on the CBC Radio show, Tales From The Vault.
The recording was from 1936 and was not the WNYC interview that I posted HERE. Until now, that 1939 interview was the only available recording of Hardeen's voice that I was aware, although he certainly must have done a lot of radio in his day (even Houdini was doing radio in the '20s).
Unfortunately, I haven't been able to turn up anything on the CBC Radio website. Did anyone else hear the interview? Let the hunt begin!