元稹《乐府古题序》谓乐府有“因声以度词,审调以节唱。句度短长之数,声韵平上之差,莫不由之准度。而又别其在琴瑟者为操引,采民甿者为讴谣。备曲度者,总得谓之歌、曲、词、调。斯皆由乐以定词,非选词以配乐也。后之审乐者,往往采取其词,度为歌曲,盖选词以配乐,非由 Yuan Zhen ”Yuefu Ancient Preface“ that Yuefu has ”due to the sound of the word, the trial to sang .As long as the number of short sentences, the difference between the rhyme level, can not help the accuracy. For citing, take the villain as a ballad .Prepare the curvature of those who always get the song, song, word, tune .Si are determined by the music, non-selection of words to the soundtrack also .After the musicians, Often take the word, the degree of song, cover selection of words to soundtrack, not by