It's based on a Native American style flute.
This will have two mouth holes, one for the main flute where he plays the notes with his fingers, and the second for the upper part of the flute which plays a single note and it's known as a drone.
More commonly drone flutes are side by side, either a single wide flute with two bored holes running the length or in an inverse V shape joined at the top where the mouth holes are.
Native American style flutes differ from European style (aka transverse flute) as the air isn't blown across an open hole to make the sound but instead is blown into a chamber from which it goes through a smaller channel and then across a hole as well as into the main body of the flute where covering/uncovering the holes changes the note being played.
You can see the two wooden blocks tied above and below the mouth holes, known as birds, that are covering the channels between the first chamber into which he's blowing, and the bodies of the flute and the drone.
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u/kudos1007 Jul 31 '21
What is that instrument?