There is always something at stake in a song. The best works pluck at futures that might be lost or gained. Even the most brazenly mass-produced and disposable tune carries within it some notion of what the world should be like. Observed in the right way, music becomes a long and constantly unfolding banner of ideas.

During times of upheaval, when the stakes are seemingly at their highest — times like the 1960s — music manages to break away from the trappings of mere entertainment and become, quite literally, a conversation.

It is easy to malign the Beatles, given their ubiquitous presence in popular music. It’s also easy to forget that the last three or four years of their career were some of the most experimental in rock up until that point. From Sgt. Pepper to Let It Be, the group exploded notions of what was and was not expected of a pop group. And with the world around them shifting so radically during the upheavals of the 1960s, their embrace of other genres, of psychedelic play, and of the straight-up bizarre and surreal fit the new environment.