The bawu (Traditional Chinese 巴烏, Simplified Chinese 巴乌) is a side-blown reedpipe found in Southern China, played by the Dai, Hani, Miao, Yi and other minorities. When in use it resembles a typical side-blown bamboo flute, but it has a triangular free reed made from brass set into the side of the pipe, surrounded by a bone mouthpiece:
This is a fairly traditional model, having a thumb hole, six finger holes, plus a tuning hole and a range of just over an octave. Unlike the ala and ding tac ta, the pipe is closed at one end. It is made from two sections of bamboo and its overall tuning can be varied by adjusting the joint between the two pieces. This is a key of G instrument and plays the scale D E F# G A B D E:
Additional pitches can be played by cross-fingering and/or half-holing and a G instrument would typically also be played in the keys of D, C and sometimes Bb.
In recent years, the rich, mellow tone of the bawu has become a favorite with composers of film soundtracks (the bawu was strongly featured in the score to "Crouching Tiger, Hidden Dragon") and many small Chinese music ensembles now feature a bawu player. "Improved" bawu have appeared over the last few decades, with increased range, plastic construction, finger keys, etc.
James Cottingham briefly discusses the physics of the bawu in his study The Asian Free Reed Mouth Organs.
The repair of bawu's free reed, in Chinese, but with lots of good pictures.
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