The five tones refer to the five tones of Gong, Shang, Jiao, Zheng, and Yu. "Lü Li Zhi" says: "The palace is in the center, and it is located in the center and spreads out in all directions. The path of singing begins with the four tones." . Shang means Zhang Ye, and things become clear. This is the explanation of the meaning of the five tones, and it is explained from the perspective of natural biochemistry and auditory sensation. The palace sound is thicker and muddier. It can be heard for a long time; the Shang sound is loud and clear, exciting and harmonious; the Jiao sound is gentle but not violent, moist but not dry, and the Zheng sound is intense and dry. It's like the sound of fire; the feather sound is round, clear, sharp and smooth, and expresses a smooth meaning; the five tones are closely related to the five elements.