Dicho, the footnote reads "Das Lied wurde geschrieben für die 1939 in Zürich uraufgeführte musikalische Dialektkomödie "Der schwarze Hecht" (eine Fassung für Deutschland entstand etwa zehn Jahre später unter dem Namen "Feuerwerk"). - Rudolf Bolli." The term "Dialektkomödie" coupled with the fact that it was written by a Zürcher and first produced in Zürich strongly suggests that it was not in German but in Schwyzertütsch, which as I noted shares some features with Yiddish that are absent from the Hochdeutch standard. (Whether mutual intelligibility is higher or lower between Yiddish and Schwyzertütsch than between Yiddish and Hochdeutsch I have no idea.)

Thanks, Pooka. I suppose a letter to the editor of Forverts might elicit something, too, though it takes me a while to write a letter in acceptable Yiddish.

Liland