LETTADLO: předpokládám, že >> A double Native American flute is a type of double flute. It has two sound chambers that can be played simultaneously. The two chambers could have the same length or be different lengths.
The secondary sound chamber can hold a fixed pitch, in which case the term "drone flute" is sometimes used. The fixed pitch could match the fingering of the main sound chamber with all the finger holes covered, or it could match some other pitch on the main sound chamber. Alternately, various configurations of finger holes on the two sound chambers can be used, in which case terms such as "harmony flute" or "harmonic flute" are sometimes used.
Extending the concept, Native American flutes with three or more chambers have been crafted. The general term "multiple flute" is sometimes used for these designs.
např.
https://www.thomann.de/cz/thomann_shaman_double_flute.htm