Marlene Dietrich always wanted to be a classical musician. Since her cabaret act and film career left little time for her to do the required practice, she played the musical saw instead. Throughout World War II she wowed USO audiences with the novelty. Here she is playing "Aloha Oe" in 1944 with the comedic setup she did in her cabaret act.
Marlene Dietrich archivist MarleneDietrichVideos also just uploaded a rare live audio recording of her performing on the singing blade in 1948.
Bonus for those who think it sounds like a theremin, here is Natalia Paruz, aka The Saw Lady, performing the Star Trek theme: