Wars often occur between tribes in the Central Plains. At this time, the Yellow Emperor defeated the Chiyou tribe and unified China. Huangdi Neijing is a classic work by China that comprehensively expounds the theory of traditional Chinese medicine. It is said that it was written by Huangdi.
People used to take notes with knots, and what they could record was very limited. Later, Cang Xie, a historian of Huangdi Neijing, was scratched by the texture of turtle's back and the tracks of birds and animals in the stars, creating characters and improving people's memory ability of things.
Legend has it that the melody was written by Ling Lun, the music official of the Yellow Emperor. Ling Lun set twelve melodies with bamboo pipes according to the call of the Phoenix. Then he determined five tones, namely: male, upper, alternating, positive and Yu.