This chapter first sets out book's purpose, which is to study the ideological, social, organizational, and symbolic attributes of twentieth-century American music. Three questions guide the investigation: (1) What are the common economic, organizational, ideological, and aesthetic traits among contemporary music genres? (2) Do music genres follow any patterns in their development, and if so, what explains their similarities and differences? and (3) Using contemporary American musical genres as a point of reference, how can we discover new genre forms and trajectories? It explores these questions in music in order to offer a comprehensive view into both classificatory schema employed to organize sound and sociocultural classification systems in general. The remainder of the chapter discusses the formal characteristics of twelve attributes found across styles of music. These organizational, economic, interpersonal, and aesthetic attributes are used to differentiate one musical style from another, and a given style from one moment in time to the next. Drawing from an inductive coding of histories of sixty American market-based musical forms from the twentieth century, it demonstrates patterns of attributes.