The term yuefu covers original folk songs, court imitations and versions by known poets (such as those of Li Bai).
[1] Furthermore, the literary application of the term yuefu in the modern sense of a classical form of poetry seems not to have had contemporary application until considerably after the end of the Han dynasty, thus adding a certain historically ambiguity due to its use in this literary sense not having occurred until centuries after the actual development of this type of verse itself.
During the Six Dynasties era, a form of yuefu using regular five-character quatrains (or paired couplets) similar to the jueju appears in the Midnight Songs poetry.
[3] Similarly, the subjects and themes of the Tang yuefu vary from simply providing song lyrics, to engaging in social satire or criticism, literary exercise, lamentations at the departure of friends, attempts to visit not-to-be-found-hermits, and romantic love in relationship to singing "girls", dancers or other professional entertainers, or the feelings of or for the ladies of the palace harems.
[4] In the Han dynasty: "Mulberry By Road" (陌上桑)， "Armed Escort" (羽林郎), "White Hair Intonation" (白头吟), "Thinking is Being" (有所思), "The Old Soldier's Return" (十五从军征), "The Peacocks Fly to the South and the East" (孔雀东南飞), In the Tang dynasty: "The Moon at the Fortified Pass (關山月/关山月/guānshān yuè) by Li Bai and the Songs of the Border (塞上曲/sàishàng qǔ) genre.