Hi, Jim. Thanks for the link to the recording by Alma Gluck. I've heard her name for many years, and now I know how she sounded.

I compared her singing to the notes on my piano keyboard, and she is indeed singing it in the key of D, and her high note is the F# at the top of the staff, a note we mere mortals probably never sing.

I suspect the tune was not written to be sung to; it was a dance tune and somebody borrowed it way back when.