In 1960, two anthropologists, Alan Merriam and Raymond Mack, noted a discrepancy in jazz scholarship. “The literature on jazz,” they wrote, “which has grown enormously in recent years, consists in the main of biographies of jazz musicians, record reviews, and analysis of the music itself. Relatively little attention has been devoted to the study of social groups in jazz and, with some exceptions, what literature exists is primarily descriptive and widely scattered.”1 Although this situation has changed significantly since Merriam and Mack first published their essay, there is still considerable debate among jazz scholars about how to account for the specific social contexts in which jazz musicians make their music, along with the relevance of various social categories for evaluating musical contents and form. Our aim in this book is to contribute to this debate by focusing primarily on jazz and improvised music collectives since World War II. Each of the chapters presents an interpretation and assessment of a specific collective or group of collectives, as well as opening up possible avenues for rethinking some of the issues involved in analyzing the social relationships and structures that make jazz and improvised music possible.