What schools are the representative works of music theory?

Yue Ji is the representative work of Confucian music theory. It opposed the view that music was only regarded as a luxury or pastime at that time, and it also opposed the view that music was simply denied. Instead, on the basis of summarizing predecessors' theories, with the viewpoint and method of simple materialism, it is proposed that music is a subjective reflection of the objective world: "Every sound starts from the human heart." When the heart moves, everything does its best. Feeling things and moving, taking sound as the shape. "That is to say," music "means that people's hearts are influenced by external things, and they have certain thoughts and feelings when they are excited, and then they are vividly expressed through sounds and dances organized according to certain laws.