Bi doi is a kind of musical instrument of airophonic family, double-reed branch of the Muong ethnic group.

It includes two joined bamboo pipes, 27.5 cm in length and 0.5 cm in diameter. Eight holes are made on the section’s body, of which seven ones are above and one is below. When played, they create enharmonic. Bi doi is used for the funeral, the worshipping and daily activities