Kayo refers to works of a poetry form with a musical nature. It is a term that refers to lyrics and its music together, and the term of poetry for singing in contrast with poetry for reciting. Kayo was always in the public realm as oral literature that was not recorded in letters.
Japanese kayo are seen among the works in "Kojiki" (The Records of Ancient Matters), "Nihonshoki" (Chronicles of Japan), "Fudoki" (records of the culture and geography of provinces of Japan) and "Manyoshu" (the oldest anthology of tanka). The kayo in the two books, "Kojiki" and "Nihonshoki", are called 'Kiki kayo'.
The poems in "Shijing", the oldest Chinese poetry book, were originally kayo, and it is known that they were accompanied with music and dance.
During the Former Han Dynasty, a music bureau called Gakufu was set up, where folk kayo were collected. From then on the works collected in this bureau and the later folk kayo came to be called 'Gafu' (yuefu in Chinese) folksongs. Chinese poetry ("Kanshi" in Japanese) became the literature for reciting, separately from kayo. The separation of poetry from songs is considered to have occurred during the Jianan period at the end of the Later Han Dynasty (Jianan literature). In the middle of the Tang Dynasty, a new kind of literature of songs and ballads called 'ci' appeared. Ci prospered during the Song Dynasty, therefore it is called Soshi (Songci in Chinese). Ci, as with shi (poetry), later came to be recited separately from music. Another kind of literature of songs and ballads 'kyoku (qu in Chinese)' appeared during the Song Dynasty, flourishing in the Yuan Dynasty (genkyoku [yuanqu in Chinese]). Qu includes gikyoku (xiqu in Chinese)(China) that is used in plays as well as sankyoku (sanqu in Chinese) that is composed of only songs and has two kinds of style, shorei (xiaoling in Chinese) and tosu (taoshu in Chinese).