While it’s romantic to imagine that Revolver was a bolt of genius that arrived without context or precedent, the reality is more interesting. Sometime in 1965, The Beatles' longtime producer George Martin quit his contract with EMI Records. Martin had been working at a flat rate, without royalties—in other words, he would’ve made what he made no matter how well the band did. Martin knew EMI wouldn’t risk jeopardizing the band’s streak, and in leaving, he essentially forced the company to pay him what he was worth. That EMI owned the studios at Abbey Road outright meant The Beatles could record more or less as much as they wanted—an opportunity that, coupled with their increasing reluctance to tour, marked an existential shift in orientation: The Beatles were a studio band now.

What was once a refuge (the band liked recording in part because it gave them a break from the fatigue of touring and public fame) turned into a hub of inspiration. Some results were obvious: the wild tape-loop collages of “Tomorrow Never Knows,” or George Harrison's guitar solo on “I’m Only Sleeping,” made during a six-hour session in which the part was transcribed in reverse by Martin, then recorded with the tape playing backward so as to make the final product sound like it was being sucked out from inside the song. Others—compression, Leslie speakers that gave vocals a liquid, sloshing quality, and automatic double-tracking capacity that allowed the band to split signals across the stereo field and give the recordings new spatial dimension—were subtler, but in all cases pointed to a supremacy of sound for sound’s sake. The pastiche of faces and lack of band attribution on the album’s cover drove home the point: For all the 300-something hours that went into the album’s recording, it’s hard to picture Revolver being made by four guys standing in a room.

While McCartney was getting more interested in characters and scenarios (“For No One,” “Eleanor Rigby”), Lennon—then starting to steep in LSD—was withdrawing into the mysteries of the self (“She Said She Said,” “Tomorrow Never Knows”). Harrison, previously a little peripheral, found not only a voice, but range: Compare the serrated R&B of “Taxman” to the Indian drones of “Love You To”—a contrast as stark as any in the band’s catalog.

In a way, it’s understandable why the album was considered minor compared to Sgt. Pepper’s for so long: Pepper’s had a rambling, mythic quality that made it seem like something more than just a set of songs, while Revolver was still essentially following the rubric of Rubber Soul—a compact set of tracks meant to show the best ideas the band had. But if Pepper’s liberated the concept of the big, sprawling rock album, Revolver still speaks to how we understand 21st-century pop: fragmented, super eclectic, each song a fully saturated mood different from the one three minutes in either direction. Where Pepper’s ambled, Revolver honored the entertainer’s timeless responsibility to grab you by the ears.

Less than a week after the album was released, the band held a press conference at the Astor Hotel in Chicago, where Lennon was inevitably forced to clarify his observation from the previous March that The Beatles had become more popular than Jesus—a comment controversial enough to be publicly denounced by the Vatican, who noted that some subjects should be respected even by beatniks. A few questions later, a member of the press noted—respectfully in both directions—that Jesus probably would have appreciated “Eleanor Rigby.” Lennon, so exhausted and troubled by the ordeal that he’d broken down in tears while preparing to meet the reporters, demurred.