The big bang: At the height of the Roaring Twenties, music scouts armed with cutting-edge recording technology set out across America to capture the unsung voices of everyday folk. Blood and soil: America's poor--cotton field slaves, mine workers, sharecroppers--find freedom through music, creating gospel, protest songs, and Delta blues. Out of the many, the one: Exotic cultures spanning America are captured on record for the first time, inventing...