Praised as "suave, soulful, ebullient" (Tom Waits), Elijah Wald is one of the leading popular music critics of his generation. In The Blues, Wald surveys a genre at the heart of American culture. It has been defined by lyrical structure, or as a progression of chords, or as a set of practices reflecting West African "tonal and rhythmic approaches," using a five-note "blues scale." He traces its roots in work and praise songs, and shows how it was...