BI duo (pinyin: bì duō hē), also known as murmur and duo, is a single-reed gas-sounding musical instrument of the Zhuang and Miao nationalities, which is popular in the vast rural areas of Guangxi Zhuang Autonomous Region and Wenshan Zhuang and Miao Autonomous Prefecture in Yunnan Province.

The timbre in the high-pitched area is crisp and bright, the timbre in the low-pitched area is thick and firm, slightly nasal, the volume is loud, and the penetrating power is strong. Often used in solo, it is a special instrument for men.

The music includes "Shepherd Boy's Music", "Blowing and Cooking", "Mumbling and Drinking", "Harvest Music" and so on.