Aren't the Vaughn Williams Tuba Concerto and the Harmonica Concerto the same piece? I seem to recall Karl Haas (hmmmm) saying that he wrote it for harmonica, and said that if nobody played it, it could be repurposed for bass tuba.

I say (hmmmm) because Karl, though a source of interesting trivia, has sometimes proven to be dead wrong, or changed his mind later and never mentioned that he once held the opposite view on some factual matter.

I mean proven dead wrong while he was still alive, of course.