It’s received wisdom that Sgt. Pepper’s Lonely Hearts Club Band, which arrived 50 years ago in the long record-breaking summer heat of 1967, is one of rock’s greatest albums. Inspired by Brian Wilson’s obsessive labor on the Beach Boys’ epic Pet Sounds, the Sgt. Pepper studio sessions were weeks of ideas tried, ideas rejected, and things tried anew. Undeniably, Sgt. Pepper is an experimental classic, a triumph of influence. But I don’t consider it even the best Beatles album; that’s Rubber Soul or Revolver. On the Sgt. Pepper album, however, is “A Day in the Life,” which is my idea of a perfect song. It is the epitome of The Beatles’ master building, of fitting stone upon stone, each section troweled together with such ingenuity and care that upon completion the whole thing feels seamless, a structure not built at all, but a whole that simply was.

“A Day in the Life” isn’t a song to sing, as are “Eleanor Rigby” (ideal for both car and karaoke), “Hey Jude” (written to soothe John Lennon’s young son, no lullaby works better at children’s bedtime), or “In My Life” (a perennial at weddings and funerals and, I can’t help mentioning, rock’s analog to Shakespeare’s Sonnet 116). Nor is “A Day in the Life” guided by melody like so many Beatles creations. It’s an elaborate production, filled with sophisticated George Martin and Geoff Emerick musical trickery (distortion, echo, dubbing, reverb). An orchestra plays, and then one singer’s voice gives way to another’s—John’s worldly reflections transitioning to Paul’s sketch of domestic memoir, and then back again—before orchestral cataclysm and a final resting place.

The song has so much happening that when I casually listen I feel the accumulated effect, but attempting to really figure out what’s going on, I fear may take the fun out of it. Liking songs is risky. They are aural fireflies, and you can get too close and lose them. If “A Day in the Life” is about anything, it speaks to the way the daily unfolding of worldly events touches the private fragilities of ordinary people. It’s Ulysses in a pop song, the typical day made unforgettable.

But here goes. What exactly is happening? In the best rock songs, you can almost see it. When Paul tells me that a girl was just 17 and I know what he means, in fact I don’t know what he means, which is the point. “A Day in the Life” is filled with a collage of images in enticing half focus. Lennon, the crowd, you, and I are all voyeurs, transfixed by something horrible, the newsworthy death. Everybody recognizes the victim but nobody knows exactly who he is. Was he a politician? When Lennon mentions the House of Lords, I always think of the Profumo scandal, which unfolded during that early-sixties period when politics began to merge with mass-media-driven celebrity in a way that undermined popular assumptions about Great Men. Whose day in the life is it, anyway? The crowd’s life or simply the singer’s? And is it still your life if your crucial experiences are received secondhand, from articles and cameras? Was Lennon himself so famous now that he was forced to live life from the passive privacy of an easy chair?

That’s how he was writing, beachcombing inspiration from headlines and news briefs in the January 17 Daily Mail, which he had open at his piano (for this song); from a circus poster hanging in his home (“Being for the Benefit of Mr. Kite”); from a cereal advertisement (“Good Morning Good Morning”); from his child’s drawing (“Lucy in the Sky with Diamonds”). In the song, the young man whose death gets noticed in the newspaper references an acquaintance of the Beatles, a Guinness beer company heir named Tara Browne, who crashed his Lotus sports car at high speed. Lennon reimagines Browne into the half-recognizable, presumably upper-class man who has it made and then throws it all away. What does it say that one crowd is transfixed by a privileged stranger’s grisly demise, but another crowd rejects a film about the achievement of a generation, the world war won? Only the singer of the song is willing to go back there, and only because he’s read the book.

You want to go back there and you don’t. A perilous, self-destructive time is being evoked, along with a sense of emptiness, the desire for substance, for something to hold on to. Lennon might be the enemy of nostalgia, but he understands its appeal—and that it is no single feeling. Lennon didn’t like his voice, but the rest of us did because, as is true in this song, it seemed to have the features of several different voices at once—intimate, seductive, raspy, bemused, distanced, and pissed off. Listening to someone achieve that much emotional overlap in sound and depth within such a concentrated amount of space is thrilling.

If “In My Life” was Lennon’s autobiographical look back on the time before he joined the Beatles, “A Day in the Life” seems to be how he experienced the quotidian as a Beatle. His conversation on talk shows and in magazine interviews revealed close engagement with current events—unsurprising, as he’s commonly remembered for the radical interludes when he took on sex, love, and the Vietnam War; remembered as the working-class hero who worried Nixon. But in this song he seems most at home as an observer, in retreat at the piano, looking out at the busy world from a housebound distance, as a creative writer would, rather than as an activist-journalist.

Some of Lennon’s songwriting contemporaries were lifting their lyrics from old blues or from overheard conversations in bars. That Lennon extracted his details from the daily throng of public images and then transposed them as, say, Philip Larkin did with his own everyday experiences means the song is his life. As Lennon eventually admitted, his activism came from guilt and obligation. He understood politics, but his outlook was artistic. I can’t think of a popular song that references more different forms of art—photography, film, literature, architecture. In that respect, “A Day in the Life” is autobiography as interior still life, a person selecting representative images to show you how he experiences the world.

And then, halfway through, he pauses and, in the celebrated phrase, he wants to turn someone else on. In the ’60s, that expression signaled Dr. Timothy Leary and LSD, especially to the BBC, which banned the song because of the drug reference. But with Lennon, who reveled in puns, wordplay, verbal sleight of hand, you could never be so literal. Maybe because I know Lennon was always ahead of his time, I hear the impulse to use the phrase the way we do now, as an omnibus for stimulation. It interests me in all respects that the line, which John called “a beautiful little lick,” was actually Paul’s, that it made Paul think of John, and that, in the song, John sings it to introduce his collaborator, Paul. “Now and then we really turn each other on with a bit of song,” John said much later, thinking back to the moment.

“A Day in the Life” makes me appreciate how close John and Paul were, how well they understood and appreciated each other as artists, how their songs came from an oscillating process of writerly separation and then joining together. It makes me see them as a little universe of invention—all those vivid images and internal rhymes turned out as casually as woodworkers with a lathe. In this respect, it’s “A Day in the Life” of a songwriting team, working alone, coming together by delivering parts to each other’s houses, helping, suggesting, competing, vitiating, and then improving, pushing each other even as each offers his own view of things. Which is exactly how they both described the writing of “A Day in the Life.”

They were different. John was sly and scathing and quick, the dark-side observer at a remove. Paul was more optimistic, taking in the bright-size of life, deeply melodic, organized, romantic, and not so funny. The song conveys some of those differences in the middle verse with Paul’s bouncy fragment of autobiography—an adolescent schoolboy waking up from a deep sleep and muzzily getting ready to catch the bus—bending toward the existential meditations of John. (When Paul runs for the bus, John supplies the heavy breathing.) The beat is now peppy with drum and snatches of piano, a common Beatles rhythm. Nothing could be more banal, getting from bed to bus, just another day in the life caught in eight perfect lines.

And then he’s smoking (something) and we are back into a (cosmic) dream, back to John with his newspaper. And what does he find? A government tally of imperfections in the surface of English roads. John’s mention of Blackburn, Lancashire, gives the song the advantage of a memorably specific place name that is in service of a more general emotion—one of those strange alchemies that just happens to work in music. Think: Paul Simon’s Saginaw in “America” or Jackson Browne’s Winslow, Arizona, in “Take It Easy” or Neil Young’s Redwood in “Heart of Gold.” That the government really was out there in Blackburn, Lancashire, and counting potholes, was the sort of activity that appealed to Lennon’s absurdist northern sense of humor.

What did it all add up to? Four thousand! What did it all really add up to? A nonsense line about the relationship between holes and Royal Albert Hall’s seating capacity. Except decay, holes, people as holes, emptiness, and audience—it’s another mystery almost seen. The feeling is rather sad. These vocal sections were written and recorded first, with the empty linking section between the first John and Paul verses counted off bar by bar. To fill the empty space, they drew on their producer George Martin’s vast musical knowledge. John wanted “a musical orgasm.” Soon enough, half an orchestra of leading London classical musicians was assembled at Abbey Road Studios with instructions to play their instruments from lowest note to highest, navigating the allotted bars at their own pace. George Gershwin’s “Rhapsody in Blue” begins with something similar, a solo clarinet glissando that was itself improvised at a rehearsal by the musician. In “A Day in the Life,” the idea was that the orchestra would slide up the scale micro-tonally, a free-form crescendo of accumulating pitches.

That recording session became a ’60s happening, with Beatles’ friends like members of the Rolling Stones and the Monkees and their sexy wives and girlfriends (like Pattie Boyd and Marianne Faithfull) turning out in the trippy regalia of the time. The orchestra wore proper dress-performance clothes. The Beatles handed out novelty-shop gag items: clown noses (for the very upstanding violins), plastic spectacles (for the more ebullient woodwinds and brass), wigs, balloons, whistles.

Paul conducted in butcher apron and groovy tie. It was a high-meets-low affair in which the Beatles took careful note of the relationship between the personalities of the classical musicians and their instruments: the violins were indeed prim and possibly high-strung; the horn players struck Paul as more fun—brassy. It was a big production to buttress the song’s big themes, and the inventive sound produced by the classicists for the rockers improved the reputations of both. They were all making music for the Everyman, and the next vocal section was Paul’s—about a guy waking up.

After John’s reprise, the orchestra returns for an even greater swelling of sound. It was like something blowing up, a tremendous wreck, the explosion of a gun inside a car. And then, after all the chaos and destruction, what next? George Harrison had suggested a fade to humming. But it didn’t work. Paul thought that the song needed firmer resolution. Three Steinway pianos and a harmonium were rolled into action, and at every keyboard the players were instructed to hit the single chord of E major simultaneously and hard, with the sustain foot pedal down, letting it carry as long as possible. There were nine takes. The tone is so big, so capacious and resonant because Martin and Emerick thought to put the recorder on half speed. It’s the sound of peace. Instead of love being all you need, here it’s music that gets you through all the days and nights.

After “A Day in the Life,” it soon became acceptable for rock musicians to strain at their songs with the same compulsion that Giacometti brought to a portrait. The Who was writing rock operas; Jimi Hendrix labored over Electric Ladyland. But the Beatles’ song didn’t just offer the permission to be a perfectionist. “A Day in the Life” created the understanding that musicians could be as ambitious about the content of rock songs as other artists were in mediums like literature and painting. In all cases, the goal is to move past literal life into the imagination to render the almost—to express the mysterious ambiguity that is more deeply life. As Giacometti told his biographer James Lord, “The more you struggle to make it lifelike the less like life it becomes. But since a work of art is an illusion anyway, if you heighten the illusory quality, then you come closer to the effect of life.” The illusion of something ordinary becomes something eternal, the forever day—and the song of a lifetime.

This article has been adapted from In Their Lives: Great Writers on Great Beatles Songs.