‘Revolver,’ Newly Expanded, Shows the Beatles at a Creative Peak

Imagine — or if you’re young or distant enough, enjoy — a moment when Beatles songs weren’t bone-deep familiar, weren’t canonical, weren’t thoroughly embedded in succeeding generations of rock and pop. A moment when the band that had worked its way up to becoming the most popular act in the Western world was still just four guys knocking songs around in a room and keeping themselves loose and whimsical. The room, however, was a well-equipped recording studio — creating what were then state-of-the-art four-track master tapes — and for all their joking around, the Beatles were also pushing themselves to evolve while applying ruthless quality control.

That’s what comes through on the expanded reissue of “Revolver,” a pivotal Beatles album from faraway 1966. Like Bob Dylan, who had gone electric with two albums in 1965 and released “Blonde on Blonde” in June 1966, the Beatles had already been pushing at the limits of what a rock song could be. But “Revolver” was a decisive step; the Beatles were determined to sound stranger and more idiosyncratic than ever.

Like previous Beatles archive reissues, the new “Revolver” set, which came out on Friday, is based on the British version of the album. Its five discs — CDs or vinyl — include the mono album and new stereo mixes along with two discs of (mostly) previously unissued studio tracks, revealing the songs as works in progress. (The two CDs drawn from the sessions are skimpier than necessary; they run only about 40 minutes each, matching the vinyl version of the set. There was room for more.)

Even an expanded “Revolver” doesn’t explain why the Beatles, already at the top of the world, were so eager to challenge themselves anew. Yet “Revolver” was, after all, an artifact of the mid-1960s, when everything was in flux and musicians were expected to be prolific. Before “Revolver,” the Beatles had already churned out six albums in Britain plus non-album hit singles, an output rejiggered into 10 U.S. releases. They had also made two movies, all tucked in between grueling tours.

Only two years earlier, the Beatles had been the Fab Four, leading the British Invasion of American pop radio. They were a charming, longhaired but neatly groomed band in matching collarless suits, smiling and wisecracking and navigating a new level of international pop success and fans who out-screamed the band’s amplifiers.

The Beatles arrived as experts on musical conventions and how to bend them. They had soaked up parlor songs, British music hall, Tin Pan Alley, 1950s rock ’n’ roll and more; they had built superb reflexes through years of club gigs. Even from the beginning, John Lennon and Paul McCartney wrote songs that slyly added unexpected chord changes and hints of ambivalence in the lyrics, sparking a listener’s reflexes and then evading them. Many Beatles songs also take an extra twist in the last few seconds, just because the band had so many ideas at its fingertips.

The Beatles and their producer, George Martin, were already pushing past teen-pop subject matter and toying with studio illusions on “Rubber Soul” in 1965. “Revolver” was not the grandly packaged, more-or-less concept album that would appear in 1967, “Sgt. Pepper’s Lonely Hearts Club Band.” But it was every bit as innovative: a clear statement that the Beatles would follow no expectations but their own.

“Revolver” opens with George Harrison’s “Taxman” — a politico-financial gripe — and ends with “Tomorrow Never Knows,” an avant-garde cosmic drone with lyrics based on the Tibetan Book of the Dead. In between are further reflections on mortality, from Eleanor Rigby’s solitary funeral to the morbid thoughts of “She Said She Said” (“I know what it’s like to be dead”). What kind of pop group was so willing to linger over death and taxes?

There were still love songs on “Revolver” — the cozily devotional close-harmony ballad “Here, There and Everywhere,” the fanfaring “Got to Get You Into My Life” — but they shared the album with the more ambiguous introspection of “I’m Only Sleeping” and “I Want to Tell You,” with the sarcastic praise of the mood-altering “Doctor Robert,” and with the chiming put-downs of “And Your Bird Can Sing.” Clearly the Beatles no longer felt they had to make themselves endearing.

On “Revolver,” the Beatles went all in on ways to skew reel-to-reel tape recordings. They started the recording sessions of “Revolver” after a four-month break — their first real respite since 1962 — and they arrived eager to experiment. Along with the elaborate overdubs they were already cramming into only four tracks, they took new delight in mechanical manipulations: loops, reversals, slowing things down, speeding things up. Band members had tripped on LSD; now they wanted to create hallucinatory sounds.

Although it ends the album, the first song of the “Revolver” sessions was its most radical: “Tomorrow Never Knows,” a pure studio construction. Its syncopated rhythm track — just one bar of Ringo Starr’s drumming and an octave-hopping bass line — is a tape loop, as are the tamboura drone and the quasi-seagull cries (McCartney’s sped-up laugh), orchestral sounds and backward guitars that waft in and out of the mix. Between Take 1 (included in the set) and the finished version, the arrangement was almost completely transformed, discarding and reinventing most of the backup track. Yet all of the studio work took only three days.

One revelation among the session tracks is the original instrumental track of “Rain,” the B-side of the single that was recorded during the “Revolver” sessions and released before the album. As recorded, “Rain” was two minutes of snappy, upbeat folk-rock, breezing through its subtle bit of asymmetry; the verse is nine bars long, not a typical eight. But for the finished song, the tape was slowed down: melting the edges of each note, making a Rickenbacker guitar sound like a sitar and muddying the ground below Lennon’s voice. At the end, his vocal is also played backward. With “Paperback Writer” on the A-side — an unlikely pop premise, a surging riff, a profusion of vocal harmonies — the single affirmed the Beatles’ mastery while forecasting change.

With a few takes of each song, the session tracks hint at how intuitively the Beatles worked. “Yellow Submarine” started out as a lament — “In the place where I was born/No one cared,” Lennon sang at first — but turned into sound effects-laden drollery. It turns out that “Taxman,” now dated by its backup-vocal references to “Mr. Wilson” and “Mister Heath,” could have had a less topical backup part, but with more syllables; the Beatles chose the terser, catchier one. For “Eleanor Rigby,” the Beatles recorded versions of Martin’s backup arrangement with a string octet using lush classical vibrato and legato phrasing, but they wisely chose a brusque, woody attack instead.

“Revolver” is also newly infused with Indian music. The link is obvious in Harrison’s “Love You To,” with its Indian modality, a sitar hook, and an Indian tabla player (Anil Bhagwat). But Eastern music also resonates in the drone of “Tomorrow Never Knows” and the guitar lines of “She Said She Said.” The Beatles were still open to influences.

The new mixes on the expanded “Revolver,” made with current technology and 21st-century ears, are a pleasure; they have more transparency and a more three-dimensional sense of space than the 1966 mixes. Yet those remixes do trade away the vintage eccentricity of the original stereo versions, which were completed in one day as an afterthought to the more fastidious mono versions, back when stereo was still a novelty.

The old stereo mixes can be heard as slapdash or as downright avant-garde. Many of the instruments and vocal tracks are heard on just one channel, pulling the music apart, particularly when heard through headphones; it’s still disorienting. The new versions are more in line with stereo-era expectations, bringing vocals and lead instruments closer to the center, but luckily without blending too much. They made me appreciate anew the loose-limbed way that Starr knocked around the beat, and the many stray eruptions of added percussion and phantom voices throughout the album.

Five decades later, it’s not easy to hear “Revolver” afresh. But the new set insists that the clearer it’s heard, the odder it is. “Revolver” still holds surprises.