The ding tac ta is a popular instrument among the Ede of the Vietnamese Highlands, similar in many respects to the ala. It consists of a bamboo pipe of about 50cm in length, with a free reed set into the wall of the pipe. The reed is made from bamboo, but it is a heteroglottal reed - ie, it is cut from a seperate piece of bamboo, then inserted into a closely fitting slot in the side of the pipe:
The pipe is then inserted into a dried gourd to form a windchest around the reed, the gourd being sealed into place with wax and the neck of the groud serving as a mouthpiece. The thumb or index finger of the right hand is used to open and close the short end of the pipe provide ornaments and vibrato; the thumb and first two fingers of the left hand are used to open and close the three finger holes.
Vietnamese Institute for Musicology has some outstanding pages on the music and musical instruments of the various minority groups of Vietnam.
A Brief History of Mouth Blown Free Reed Instruments
What Is A Free Reed?
Origins Of The Free Reed
Eastern Free Reed Instruments
A Selective Discography Of Asian Free Reed Instruments
Western Free Reed Instruments
Bibliography