This paper introduces the various types of music manuscripts and current issues in music sketch studies. It argues that the study of musical manuscripts is not simply the direct conversion of composition processes into music analysis. Nor is it limited to the function of providing a basis for choosing performance editions. Rather, it allows the researchers to weigh and ponder on many entangled issues, such as the composer's intentions, musical influences and music trends, composition habits, manuscripts chronology order, revisions to the draft, and traces of pre-composition plans. In addition, manuscripts could be situated in the network of various cultural or historical moments, and of a variety of musical styles and trends. It can be linked to a large web of associations contributing in different ways to the production of the manuscripts. Manuscripts are deeply rooted in historical processes and are essentially open text. The diversity of the twentieth century music manuscript, both in terms of musical language and medium, also raise new issues for sketch studies. Borrowing from Philip Gossett, this paper examines three areas of manuscript studies—confirmatory, suggestive, and conceptual—to ponder on the analysis of 20th century music. From this angle, the paper analyzes the manuscripts of Taiwanese composer Lu Yan. It focuses on several diagrams of integers in the composer’s sketches. In particular the paper examines how these diagrams reflect abstract conceptualization of pitch structure and harmony language, and how they are connected to his composition, “Woodwind Quintet.” These sketches of “pitch material” illustrate the profound thinking encompassing his harmony, melody and tone row and balanced relationship of sound world.