I had always known incorrectly assumed (see here) that "Cosme McMoon" was a nom de plume (nom de klavier?) of a well-known New York pianist of the time. However, at the end of an interview transcript from WCLV Cleveland (which was copied to a mailing list that somehow ended up on the archives of the UC Davis site) , Paul Moor states that Cosme McMoon was actually the well-known pianist Edwin McArthur, also known for his work with Kirsten Flagstad. From Moor's account:
I'd heard before that McArthur had played for Mme Jenkins at the beginning of his career, but had never taken it seriously. I can only assume that at the time he, as any musician can understand, simply needed the scratch. The discovery of Cosmé McMoon's true identity set me on fire to get into contact with him, and ask him some probing psychological questions about her rare disorder. Unfortunately, I learned from Grove's Dictionary of Music and Musicians that Edwin McArthur had already died, at the age of 79, on February 2, 1987. I still marvel at the sublime serenity of his facial muscles the only time I heard him and Mme Jenkins together. At that time I had the feeling that nothing short of an atomic explosion would have ruffled his extraordinary aplomb.The interview with McArthur/McMoon is fascinating, and sheds light on the FFJ phenomenon and how the New York audiences were able to create the mystique of a great artist in a singer
Q. In what way was the audience able to contain itself, or to maintain some semblance of approval during all this, Mr. McMoon?You can read the entire interview here. Those eager to sample the
A. Why, there wasn't any question of semblance of approval, because they approved of it wholeheartedly, but the audience nearly always tried not to hurt her feelings by outright laughing, so they developed a convention that whenever she came to a particularly excruciating discord or something like that, where they had to laugh, they burst into these salvos of applause and whistles and the noise was so great that they could laugh at liberty.