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I know we’ve discussed this idea before, so I wondered if anyone had seen or played these? He call them flutes, but from the description they’re fipple flutes.
Mack Hoover is always showing me one or another of the ones he has made. You might ask what he has on hand at the moment.
I know for sure that he has a really neat set of Ski pole whistles right now.
They’re walking stick NA flutes, appears to me. They are essentially fipple flutes.
Goll, Martin, I was sure that someone had captured some actual “walking stick” bugs and had turned them into whistles. 
What a picture I had in my mind! It took a minute to realize you meant an actual “walking stick” or cane. 
Wouldn’t I love a such whistling photographer’s monopod… 
Like this NA walking stick flute :
See the story, details here: