Mr. Yu is a single-reed gas-sounding instrument of the Jingpo and De'ang peoples. In Jingpo language, "Bi" is a general term for air-sounding musical instruments, and "general" means double, which means a pair of air-sounding musical instruments with parallel pipes. Folks have the same style but different specifications.

The Bi always consists of two sound tubes and reeds of different lengths and thicknesses. The sound tube is made of bamboo, with a copper reed at the head. The long and thick one is the main tube. There are six (front five and one rear) circular sound holes on the tube body, which can emit seven melodic tones, short and thin. For the auxiliary tube, only the reed is set, the sound hole is not opened, and only the barrel sound is emitted. In some areas, a small gourd-made resonator is often placed at the end of the main pipe, which can make the sound extraordinarily rich.