It starts from the Confucian view that
礼 'rites' set people in their places and
乐 'music' brings them into harmony, then traces the court music of the Han: Emperor Wu's
乐府, which collected songs from across the empire, and the hymns sung at the great sacrifices, whose words survive because the treatise copied them. One hymn, on the sun, moon, stars and five phases, gives
周而复始 'round and back to the start'.
