The Beatles’ “Sgt. Pepper’s Lonely Hearts Club Band” album was hailed in some quarters as a groundbreaking milestone in popular music on its release in June 1967.

Others scoffed at it as an overly ambitious bid for artistic respectability that abandoned the innocence of the group’s early hits.

In the ensuing five decades, the debate has raged on and is likely to gain renewed fervor with the Friday release of the 50th-anniversary edition of the album, newly remixed in stereo by Giles Martin, son of the album’s original producer, George Martin.

The raison d’être for the project isn’t simply to serve up a new edition of a classic album that scads of Beatles fans are likely to lap up — though clearly many will.

Rather, it is an attempt to rectify what’s long been perceived as a significant though hardly fatal flaw in the original stereo version, created with considerably less time and attention from band members Paul McCartney, John Lennon, George Harrison and Ringo Starr.

It’s hoped that the new iteration will introduce the work to younger audiences and sound more akin to contemporary recordings.

“It’s not exactly an album that is unloved,” Giles Martin, 47, said during a recent playback session at Capitol Records’ Studio A in Hollywood for music writers and a couple of dozen executives and employees of Universal Music Enterprises, the parent company of Capitol, which is releasing the album in the U.S.

In late 1966 and early 1967 when the Fab Four set to work on “Sgt. Pepper” as the follow-up to “Revolver,” monaural sound was the dominant format for music.

Stereo counterparts often were created hastily for the U.S. and other foreign markets. Because the “Sgt. Pepper” stereo mix was better known in the U.S., Lennon once famously stated, “You haven’t heard ‘Pepper’ until you’ve heard the mono version.”

In part that’s because the group’s vocals are often divorced from the instrumental accompaniment, separated in different channels because that was how the engineers who created the stereo version could get the job done quickly.

Just how quickly? George Martin and the Beatles spent about three weeks mixing the mono version; its stereo counterpart was completed in barely two days, according to Giles Martin’s chief collaborator on the new edition, Abbey Road Studios senior engineer Sam Okell.

“There is a thing about the mono mix,” Martin said. “There is immersion that comes from the depth they put in there, even though it is just coming out of one speaker. I was trying to create that (in stereo). No one can say the (1967) stereo mix is not a great-sounding record. But there’s a way to get the best of both worlds.”

Feedback on the new mix has been “almost humiliatingly positive,” Martin said.

Chris Carter, host of the long-running “Breakfast With the Beatles” radio show on L.A. rock station KLOS-FM, says: “In general, I was blown away. Not to sound overly dramatic or corny, but in a lot of ways it was like hearing the record for the first time.

“What really struck me is that the Beatles intended to be perfectionists on this record.”

WHAT DOES IT ‘SAY TODAY’?

PBS is getting in on the “Sgt. Pepper” 50th with a new documentary, “Sgt. Pepper’s Musical Revolution,” premiering June 3 and hosted by composer, music historian and documentarian Howard Goodall.

“I know it’s a landmark in terms of pop culture, the Summer of Love, youth culture, the’60s,” Goodall said, “but really what I’m interested in is: What does this music say today? Why has it been treated with such respect for 50 years?”

Goodall, who like many Beatles fans said he might cite “Revolver” or “Abbey Road” rather than “Sgt. Pepper” as his favorite Beatles album, nonetheless unhesitatingly calls “Pepper” “their most important album.”

Said Goodall, “When someone 20 years old says, ‘Why do people your age think it’s such a big deal?’ I would say that in our modern musical world, the eclecticism of ‘Sgt. Pepper,’ the broad expanse of styles, genres and sounds, is not such a big deal.

“But,” he continued, “for those of us who listened to it when it came out it was a big shock to the system.”

Greg Harris, executive director of the Rock and Roll Hall of Fame and Museum in Cleveland, noted, “Stylistically they were throwing garage rock in with music hall with Indian ragas.

“One of the other amazing things for me is that it’s a full-on album that takes listeners on a journey, but it’s also filled with these incredible songs that can stand on their own.”

CD, DIGITAL OR VINYL?

“Sgt. Pepper” represents the most elaborate reissue yet of an individual Beatles album. It’s being offered in several configurations: on CD, digital and on vinyl — the last in a half-speed mastered pressing that ups the audio fidelity one more notch and is accompanied by a second LP containing alternate mixes of all 13 “Sgt. Pepper” songs as selected by Giles Martin.

A six-disc deluxe set includes the new stereo mix and the mono mix of the album on CD with two more CDs containing dozens of outtakes, alternate versions and studio chatter, plus a Blu-ray and DVD including a 1992 documentary on “The Making of Sgt. Pepper” created for the album’s 25th anniversary but never released commercially.

It also comes with a 145-page book with artwork, handwritten lyric sheets, essays, photos and detailed session information on each of the songs.