Hornbostel - Sachs
Flutes with external duct
The air itself is the vibrator in the primary sense. The standing waves are significantly confined within the instrument itself. In each flute, a narrow duct directs the air stream against the sharp edge of a lateral orifice. The duct is outside the wall of the flute; this group includes flutes with the duct chamfered in the wall under a ring-like sleeve and other similar arrangements. The flutes are joined to form a set. Tibet.
Sets of flutes with external duct