Rhyme & Couplets is about matching word to word and sound to sound. The upper and lower lines are of equal length, with word matched to word and sound to sound, level and oblique tones alternating, and allusions often used. The class covers idioms, couplets and the tonal rules of parallel prose.
In the Yongming years of the Southern Qi (about 489), Shen Yue and others set out the four tones and eight faults, and parallel prose and poetry became conscious of their tonal rules and parallelism.
Meng Chang of the Later Shu wrote on a peach-wood charm "The new year receives abundant blessings; the fine festival is called Everlasting Spring", said to be the earliest spring couplet.
Rhyme & Couplets is the class in the chapter on Letters on the tonal rules and parallelism of Chinese, covering idioms, couplets and the tonal rules of parallel prose. Word is matched to word and tone to tone, level and oblique tones alternate, and allusions are brought in, and so the symmetry of the language shows.
