How does this Overtone Flute/Koncovka I just made sound?

My Website As a Instrumentmaker: https://www.fujaraflutes.com/
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You can hear me playing a small sized overtone flute called 'koncovka' in key of D.
I made it out of a small trunk of Black elderberry wood a couple of weeks ago.
These flutes have no playingholes, you can play different notes simply by changing the airpressure and opening and closing the end of the tube!
'Two minutes to learn, a lifetime to master' they say :)

Видео How does this Overtone Flute/Koncovka I just made sound? канала Winne Clement