Throughout the Thanksgiving and Christmas holidays in 1963 America mourned for their fallen president. As the new year dawned, the sadness of the previous autumn was driven away when the music of the Beatles arrived in America. By January 1964, "I Wanna Hold Your Hand," was blasting out of millions of record players and car radios. In February, when the Beatles appeared on the popular Ed Sullivan Show, more than half the television sets in America were tuned in to watch. And the Beatles introduced more than just well-crafted, energetic rock songs. They also had what was considered at the time to be long hair. Almost overnight, tens of thousands of American males let their hair grow long and picked up guitars to form their own Beatlesinspired rock groups.

As the lilting harmonies of the Beatles became the soundtrack for the sixties, folk musicians...