"In the sound of the 1960s and 1970s, nothing symbolized the rift between black and white America better than the seemingly divided genres of country and soul. Yet the music emerged from the same songwriters, musicians, and producers in the recording studios of Memphis and Nashville, Tennessee, and Muscle Shoals, Alabama -- what Charles L. Hughes calls the country-soul triangle. In legendary studios like Stax and FAME, integrated groups of musicians...