It was 70 years ago today (well, June 2 in the United States) that an imaginary English musician named Sgt. Pepper taught his band to play and, 20 years later on that same date, the Beatles released an album about it that set the music world on fire.

“The sound of Sgt. Pepper’s Lonely Hearts Club Band changed the way listeners connected with music,” says Donna Parsons, a lecturer in the University of Iowa School of Music and an expert on pop music, the Beatles in particular. “The record label never released a single, but it was so groundbreaking that radio stations played it in its entirety. Its revolutionary status was rooted in the nature of experimentation and the science of sound, creating a must-hear cultural cornerstone.”

For better and for worse, the album turned pop music into art, says Kembrew McLeod, professor of communications studies and a pop culture historian who teaches the class Cultural History of Popular Music.

“It expanded the sonic and lyrical possibilities within the context of popular music, but it also opened the door to rock and roll excess that came to dominate music and made rock a lot less fun in the years to come,” he says.

Despite being Sgt. Pepper aficionados, neither McLeod nor Parsons has any memory of the album’s rapturous 1967 reception, as he was not yet born and she was only a few months old. But Parsons does remember spending childhood afternoons sitting in her brother’s bedroom in Norwalk, Iowa, listening to the record for hours.

“It’s inhabited with so many colorful characters and distinct places, and creates these incredible dreamscapes,” she says. The lyrical depth, instrumental sophistication, and avant-garde production mean “there’s so much here that you have so many ways to listen, depending on how you want to listen.”

Both professors use the Beatles’ music in their classes, in particular Parsons, who has made the band’s magnum opus the focus of much of her academic and teaching work. A pop music expert, she teaches The World of the Beatles in the UI School of Music and has discussed the band and its music in appearances on Iowa Public Radio and at forums in Iowa City and Des Moines. She’s participated in academic conferences about the Beatles in Liverpool, at the University of Pennsylvania, and this year at the University of Michigan on June 1. She’s visited Liverpool, the band’s hometown, 11 times for research—her office wall is lined with dozens of photos that she’s taken of prominent Beatles landmarks in the city—and she’s working on a book, The Beatles; Fervor, Fandom, and the Cultivation of a Legend.

The more Parsons learns about the Beatles, the more she loves them.

“Every album challenged listeners to redefine preconceived notions of popular music and its power to transform lives,” she told the Daily Iowan in 2014. “Musically, the Beatles raised the bar so high with the quality of their songwriting, their musical experimentations, and their ability to create albums that still speak to our hopes and concerns. They remind us that many of the boundaries we encounter are ones we have self-imposed. The Beatles taught us to never let go of our dreams or our desire to attain the impossible.”

And none did that more than Sgt. Pepper. Taking a cue from Pet Sounds, Brian Wilson’s experimental tour de force with the Beach Boys released a year earlier, John, Paul, George, and Ringo, along with producer George Martin and engineer Geoff Emerick, used recording technology advancements to create sounds at once old fashioned (the music of an Edwardian brass band) and contemporary (the drug-influenced lyrics). It took months to record and featured discordant orchestral arrangements, calliopes, echo chamber vocals, sped up and slowed down recording, double tracking, and other studio tricks to create odd tones and warped melodies that seem to manipulate time.

“These were soundscapes that no one had ever heard before,” says Parsons. “They spent 700 hours in the studio on this album to get those sounds right.”

Compare that, she says, to recording 10 songs in 12 hours, as the band did during one of their earliest recording sessions for their first album, Please Please Me.

Parsons says the lyrics on Sgt. Pepper achieved a level of poetry rarely found in rock and roll at the time. They showed the group maturing from its early, teenage love songs (“I’ll tell you something/I want to hold your hand”) to sophisticated, adult love songs (“I want her ev’rywhere, and if she’s beside me I know I need never care”), to…well, whatever “tangerine trees and marmalade skies” is about.

“The lyrics required more critical thought from the listener, to figure out what it’s about,” Parsons says. “Nobody was used to hearing pop songs that start with the words ‘I know what it’s like to be dead,’” as “She Said She Said” does, a song from Revolver, the Beatles’ previous album, which foresaw some of the growth of Sgt. Pepper.

Parsons says she thinks Sgt. Pepper became such a phenomenon because, ultimately, it’s a wistful look at lost youth, when life was simpler, a universal longing. For the Beatles, that was a time before Beatlemania cut them off from the world, remembering their childhood in an industrial town that had seen better days (“Strawberry Fields Forever,” which came from the Sgt. Pepper recording sessions), the mundanity of getting up in the morning (“A Day in the Life”), or imagining what would motivate a teenage runaway (“She’s Leaving Home”).

“It’s all about their childhood, but they talk about it vaguely enough that it speaks to all of our childhoods,” Parsons says. “The storytelling takes you into another world, but you’re safe there; it’s a sanctuary. It gives you a place where you can figure out who you are and what you want to do.”

But McLeod wonders how long Sgt. Pepper will be seen as a cultural barometer. The music, after all, sounds very much dated from the psychedelic 1960s, while other Beatles songs still sound fresh and timeless today.

The album also has little staying power with subsequent generations that were raised mostly on hip-hop.

“Within contemporary pop culture, it doesn’t stand out as a touchstone with young people,” he says, noting that while most of his students know who the Beatles are, he can’t remember any of them asking about Sgt. Pepper. “But it’s still important because it established the album as a single, cohesive work of art and not a collection of singles. Its legacy is still felt by young people who may have never even heard of it if they’re invested in the idea of an album as a single unit making a statement.”

Fifty years on, Sgt. Pepper has gone through the critical revisionary analysis common to so much great art. Some conclude it to be too technological, overwrought, clinical, precious, and, in many cases, overrated. Considered for many years the best rock and roll album ever recorded, many critics now don’t even put it at the top of their list of best Beatles albums ever.

McLeod and Parsons agree there’s merit to that reassessment. Parsons now ranks Rubber Soul and Abbey Road above Sgt. Pepper on her list of favorite Beatles albums, while McLeod’s favorite is Revolver. His primary criticism is that by creating the notion that rock and roll can be art, Sgt. Pepper gave birth to the music snob.

“After Sgt. Pepper, critics and audiences began to look down on music that they considered meaningless fluff,” says McLeod. “It created this division between music that is capital-A art and other music. Even the Beatles’ own earlier music is often dismissed as commercial fluff. They really were the first boy band, but that’s now seen as diminishing their early music, even though it stands up as important a cultural artifact as Sgt. Pepper.”