The purpose of this thesis is to provide translation of documents on lu from two primary sources for a study of the theory of ,lu, with the main focus on the interpretation and the signification attached to each of the twelve lu-pitch names. To establish the background information of the lu-10 system, an explanation of its acoustical properties is first presented. Based on the most important and widely used tonal system in ancient China -- the san-fen-sun-i system, the illustration is provided for the process of tone generation. Methods proposed by the main theorists who engaged in the discussion of the system of lu are presented. The introduction of the concept of yin and yang in reference to the twelve lu and the signification of the lu-lu system in relation to the human and natural world will also be discussed. The main body of this study is devoted to the translation of written references on the meaning of the twelve lu. The first part is the translation of the selected passages from The Anthology of the Historical Document of Ancient Chinese Music. edited by Tsai-Ping Liang; the second part is the translation of a modern exegesis from an article written …