Hornbostel - Sachs
Sets of open flutes with internal duct without fingerholes
The air itself is the vibrator in the primary sense. The standing waves are significantly confined within each flute, where a narrow duct directs the air stream against the sharp edge of a lateral orifice. Two or more pipes with open end are combined with two more more pipes with closed end. The instrument has no fingerholes. Organ with both open flue and Rohrflöte stops.
Sets of open flutes with internal duct without fingerholes combined with set of partly-stopped flutes with internal duct