Metre (poetry) of over some two-and-a-half millennia. Beginning with the earlier recorded forms: the Classic of Poetry tends toward couplets of four-character lines, grouped in rhymed quatrains; and, the Chuci follows this to some extent, but moves toward variations in line length. Han Dynasty poetry tended towards the variable line-length forms of the folk ballads and the Music Bureau yuefu. Jian'an poetry, Six Dynasties poetry, and Tang Dynasty poetry tend towards a poetic metre based on fixed-length lines of five, seven, (or, more rarely six) characters/verbal units tended to predominate, generally in couplet/quatrain-based forms, of various total verse lengths. The Song poetry
Regulated verse are rhymed on the even lines, with one rhyme being used throughout the poem. Also, and definitionally, the tonal profile of the poem is controlled (that is, "regulated"). Furthermore, semantic and tonal parallelism is generally required of certain interior couplets. During the Tang Dynasty, the "Shen-Song" team of Shen Quanqi and Song Zhiwen greatly contributed to the development of this Classical Chinese verse form. Regulated verse consisting of the three "jintishi" or "new style poetry" forms of "lushi", "jueju", and "pailu" while retaining the basic characteristics that are distinguished from the "gushi" or "old style poetry" by the addition of