I Hear a Symphony opens new territory in the study of Motown's legacy, arguing that the music of Motown was indelibly shaped by the ideals of Detroit's postwar black middle class; that Motown's creative personnel participated in an African-American tradition of dialogism in rhythm and blues while developing the famous "Motown Sound." Throughout the book, Flory focuses on the central importance of "crossover" to the Motown story; first as a key concept in the company's efforts to reach across American commercial markets, then as a means to extend influence internationally, and finally...