Answering my query, Hans Eekhoff says he has the non-vocal German Brunswick of Ray Miller's "Mississippi, Here I Am." It's got more hot Muggsy, but no sign of Mystery Guy. Aaahh, nuts. Well, it never hurts to ask!*
*incident in the life of four-year-old George S. Kaufman:
George's Mother: "It wouldn't hurt to be nice to your Aunt Matilda."
George: "That depends on your threshhold of pain."