Harmony and coordination. In the Southern Song Dynasty, the world spoke a new language, and Xun Xu was good at explaining the sound. Liu cited "A Brief History of the Later Jin Dynasty and Xun Chu of the Jin Dynasty": "The warehouses of various counties, or the clocks used in the Han Dynasty, were all answered without knocking, and the sound was harmonious." "Cloud Seven Signs" Volume Seven: "The combination of sound and rhyme makes jade true."