Aha! a new interpretation. Not just what's the oldest type of instrument, but the oldest example.

It's not a new interpretation, it's what I had in mind from the start of this thread.

Chinese bells and cymbals go back about 4000 years - are any bronze instruments from the Shang dynasty still played for real music?

The oldest instrument I've got is an English double whistle in walnut from about 1820, which doesn't quite work right - I'm progressively rebuilding the fipple out of layers of superglue.