During the 1950s and 1960s, when Pete Seeger and Malvina Reynolds coaxed classrooms full of kids to join them in the singing of folk songs, no one paid much attention—not even those who, in the middle of the Cold War, saw America's "singing left" as a threat to the republic. "They never thought there would be a problem with Pete Seeger singing to six-year-olds," Seeger's biographer, David King Dunaway, wrote. But considering the baby boom those six-year-olds turned out to be, Dunaway's later observation made sense: What was in the offing was "an American folk music revival that I think we have to give the FBI credit for helping to establish."

The law of unintended consequences gave a quirky twist to the relation between the Old and New Left and, in the process, lent peculiar accents to America's musical and political culture that we can't seem to get rid of even today. The folk revival—a fad sandwiched between the beatniks and the hippies—may have been brief, but it was also the baby boomers' coming of age, and its echoes have been lasting. Bruce Springsteen made a splash in 2006 with his Seeger Sessions. Ry Cooder paid homage to Woody Guthrie in the 2007 release My Name Is Buddy. Sheryl Crow told Billboard magazine that her song, "Shine Over Babylon," is "very environmentally conscious, in the tradition of Bob Dylan."

That means, of course, that, in investing so much meaning in their pop-culture favorites, the baby boomers have more than a little in common with their predecessors.