The pen tube is a clarinet air-sounding instrument unique to the Buyi people, named for its slender shape similar to that of a writing brush.

When playing the pen pipe, both lips contain the first and second reeds, the end of the pipe is horizontal to the right, hold the pipe with both hands, press the first and second holes of the tail with the middle finger and index finger of the right hand, and press the third hole with the index finger of the left hand, and use the circulatory ventilation method. Blow the air drum spring to pronounce, often rocking the body to help its performance.

When the three holes are fully pressed, it is pronounced as a, the first hole is opened as c1, the second hole is opened as d1, and the first and second holes are opened at the same time as g. The pronunciation of the pen tube is quite special. Its barrel sound is not the lowest g, but a. Its third hole is not actually pronounced, and is only used to control the sound quality of the lowest sound. When the first and second holes are opened, the g sound is emitted. When there is sand sound, the third hole can be opened at the same time, and the third hole has no effect on the treble c1 and d1.

Since the pen barrel has fewer sound holes, it can only emit four notes, and the sound range is only fifth. Players with better blowing skills can play six or seven notes with the overblown method.