Turn on the radio or take the time to flip through the stacks of used CDs at your local thrift store. Google "rock 'n' roll music," even. Better yet, visit any public place that plays popular music from the last 50 years or so as the soundtrack to your Saturday afternoon grocery-shopping, clothes-buying or indie record store-scouting experience and you'll find that no matter where you go, there's an ever-enduring presence that since the late 1960s...