If we can credit a single artist with electrifying American blues, it’s T-Bone Walker. In the late ’30s and early ’40s the guitarist plugged in and pioneered a jazzy, amplified style that has loomed over every player ever since—fellow titans B.B. King and Albert King included. Walker was ahead of the game; after all, electrification didn’t become widespread in blues music until a decade later, during the postwar years. That’s when African-Americans started moving to cities for factory work and the country’s power grid rapidly expanded. Electricity, it should be stressed, didn’t just make the music louder; it opened up new modes of expression that would be developed for generations to come. You can hear this most clearly in the Chicago scene, where Muddy Waters, Howlin’ Wolf, Elmore James and others invented a throttling heaviness and distortion-soaked anguish that radically made over the country-blues tradition from which they had emerged.