VIET NAM (Vietnam bamboo flute) is a horizontal flute with six holes that are evenly distanced so as to give the pentatonic scale. The pitches obtained, therefore, are different from those of the tempered scale; for instance, the Vietnamese F note is higher than the natural F and lower than the F#. The Western flutes use metal keyes whereas the Vietnamese flute uses fingers to stop the holes and open them in various ways, thus creating different effects. The disadvantage of the Vietnamese bamboo flute, however, resides in the fact that one cannot go too fast on the semitones which would get them blurred with other notes. What has been done to overcome this difficulty is that five secondary holes have been perforated so as to allow the expression of such subtleties. In the process, this allows for the playing of Western classical music as well.
Courtesy Vietnam Datacommunication Company (VDC) and Vietnamese Institute for Musicology (V.I.M)