Qu are poetic musical song lyrics with lines of varying longer and shorter lengths; which are set according to certain specific, fixed patterns of rhyme and tone, based on a set of conventional musical pieces, after which the matched variations in lyrics (or individual qu poems) are based and after which they generally take their name[1]. In Chinese literature, qu (Chinese: 曲), or yuanqu (元曲) consists of sanqu (散曲) and zaju (雜劇). The san in sanqu refers to the detached status of the qu lyrics of this verse form: in other words, rather than being embedded as part of an opera performance the lyrics stand separately on their own. Together with the various shi and fu forms of poetry, the ci, qu, and the other fixed-rhythm type of verse comprise the three main forms of Classical Chinese poetry. Since the Qu became popular during the late Southern Song Dynasty, and reached a special height of popularity in the poetry of the Yuan Dynasty, therefore it is often called yuanqu (元曲), specifying the type of qu found in Chinese opera typical of the Yuan Dynasty era. Both sanqu and ci are lyrics written to fit a different melodies, but sanqu differs from ci in that it is more colloquial, and is allowed to contain chenzi (襯字 "filler words" which are additional words to make a more complete meaning). Sanqu can be further divided into xiaoling (小令) and santao (散套), with the latter containing more than one melody.