To anyone who grew up in the period, this is a bit absurd. Of course the rock revolution was real; of course the rock era was an era, with signatures and styles all its own. The first song that the Beatles sang was self-composed, in itself a huge change. By 1967, when “Lucy in the Sky with Diamonds” and Bob Dylan’s “Visions of Johanna” were wildly popular, the musical world had become completely different from what it had been a few years earlier. Still, attempts to dissolve a period, however unpersuasive, can be instructive, because they make you think hard about what a period style is. Your common sense goes to war with your critical theory—as it should, since the point of critical theory is to puncture what we call common sense, while the point of common sense is to see past theory to things as they are.