There are four quatrains in each sentence, five words in each sentence and seven words in each sentence.
Ancient poetry: The original meaning of "ancient poetry" refers to the poems written by ancient literati. Before and after Wei, Jin, Southern and Northern Dynasties, there appeared a number of five-character poems written by scholars before Wei and Jin, which had no title and no author. Most of them are lyric poems with unique expressive techniques and artistic styles, which are collectively called "ancient poems".
Yuefu poetry is mainly composed of five words, seven words and miscellaneous words. The sentence pattern is flexible and free, the language is natural and fluent, easy to understand, catchy and full of life breath.
In other words, Yuefu poetry is very casual.
Rhymes and quatrains are very rigorous. There are rules for the rhyme and number of words in flat tones.