In the course of my research into the pan flute's history, I have always striven to represent two facets of historical perception: the historical viewpoints of the people who originated the various pan flute forms, and the conclusions and classifications of researchers. In the case of the Vietnamese crenh (also called khen or khene), there are differing evaluations as to whether the crenh can be classified as a true pan flute form (view a video clip of a crenh player).
The Mong people of Vietnam account the crenh as a pan flute form, primarily as a result of their unique traditions with the instrument, as well as their perceptions of the similarities between the crenh and other pan flute forms. However, the majority of researchers regard the crenh as a member of the free reed family of instruments, and other pan flute forms are regarded as aerophone-type woodwind instruments. The construction of the crenh is inherently different from other pan flute forms in that it employs an integrated air chamber and finger holes.
These two different perceptions of the same instrument are certainly in contrast to one another, but I submit that each viewpoint is equally valid within its own canon of criteria. To understand both positions is to better understand the crenh. -Douglas Bishop