Beatles fans who favored John Lennon’s most deeply personal songs – “Julia,” “I’m a Loser,” “Help!” – could scarcely have imagined the searing introspection Lennon would unleash with his first post-Beatles solo album. Released in December 1970, Plastic Ono Band gave new meaning to so-called confessional songwriting. Framed by rock’s most basic instrumentation – bass (played by Klaus Voormann), drums (played by Ringo Starr) and guitar and piano (played by Lennon himself), the former Beatle presented himself in all his myriad guises, from angry rebel to devoted soulmate to questing artist striving to free himself from the shackles of Beatledom.

Most striking, however, was the blood-letting expressed in songs rooted in traumas Lennon had experienced in his childhood and adolescence. In the rock world, art as therapy had never been so fiercely applied.

The spark for Plastic Ono Band’s red-hot glow can be traced to a book Lennon discovered in March of that year. Titled The Primal Scream, the book put forth the thesis that nearly all neurotic behavior could be traced to traumas endured in childhood. Dr. Arthur Janov, the California therapist who had written the book, had devised a therapy designed to, in Lennon biographer Philip Norman’s words, “break down the force of years of compressed feelings by taking the patient back to childhood to confront the pain.” The therapy literally involved screaming, or articulating repressed pain as “primally” as a newborn that has just emerged from the womb.

For Lennon, Janov’s therapy linked up with uncanny precision to his own troubled past. Forced at age six to choose between his separated parents, he selected his mother. She subsequently abandoned him. A decade later, just as Lennon was re-establishing a connection with his mother, tragedy struck when she was fatally hit by an automobile. In subsequent years, Lennon often said he lost his mother not once, but twice.

By the time Lennon entered EMI’s London studios to record Plastic Ono Band, he had submitted himself to Janov’s treatment in both private and group sessions. Coupled with the recent, nasty breakup of The Beatles, the therapy brought a gamut of raw emotions percolating to the surface. In typically unflinching fashion, Lennon was determined to capture those emotions in songs and music. Speaking years later to Rolling Stone, Voormann said, “As soon as we came into the studio, we noticed that he was very much taken by that experience he went through [with Janov], and he wanted, as quickly as possible, to get this feeling down before it changed. That was his main thing.”

In keeping with the rawness of those emotions, Lennon also wanted to steer clear of the lush production style he associated with George Martin. Therefore, most of the tracks were recorded in one or two takes, with producer Phil Spector doing mixes at the console as the band recorded. As players, both Starr and Voormann were masters of elegant simplicity, and each of them eschewed any hint of musical gaudiness. Both men locked in with Lennon’s guitar to create a sonic intimacy that made listeners feel like the proverbial fly on the wall.

“There are a lot of mistakes on there and timing changes,” Voormann said, “but it was just like a pulse, which was exactly what John wanted. He loved it.”

Few albums have opened in more haunting fashion than Plastic Ono Band. Inspired by the mournful toll of a church bell in a British Hammer horror film, Lennon rang in the opening song, “Mother,” with a series of somber, dirge-like chimes. “Mother, you had me but I never had you,” he sings. The track culminates in shrieks of “Momma don’t go/Daddy come home” borne straight from Janov’s prescribed therapy. Singing without the sonic embellishments or vocal distortions he had often used in The Beatles, Lennon comes off as more exposed and vulnerable than ever before.

Indeed, anger, vulnerability and repudiations of what Lennon regarded as false hero-worship course throughout the album. The lilting “Hold On” posits haiku-like reassurances to Yoko (and to the world at-large) in the face of post-Beatles backlash. Similarly, “Isolation” asserts that he and Yoko are “just a boy and a little girl trying to change the whole wide world” while that “little town” of a world is trying to put them down. “Working Class Hero,” performed alone by Lennon with just a strummed acoustic guitar, is essentially a scathing folk song that castigates the forces that shaped him.

Along with “Mother,” Plastic Ono Band’s most seminal tracks are “Love” and “God.” In addition to sporting a wistful, fragile vocal employed previously only on “Julia,” from “the White Album,” “Love” sounds in some ways like a broken-glass template for “Imagine.” “God,” on the other hand, lopes along in what would seem a resigned and casual manner, were it not for the litany of powers and people (including The Beatles) whose hold and authority Lennon vehemently rejects. Fittingly, Plastic Ono Band concludes with a horrifying nursery rhyme, “My Mummy’s Dead,” that’s as grim as anything the Brothers Grimm might have conjured up. Recorded in demo fashion, and sung in the voice of a dazed child, the song serves as the perfect bookend to “Mother.”

Given its unfettered content, it’s hardly surprising that Plastic Ono Band didn’t fare especially well in the marketplace upon its initial release. George Harrison’s triple-album opus, All Things Must Pass, was released at roughly the same time, and that set (along with Harrison’s monumental hit, “My Sweet Lord”) stole much of the Lennon album’s thunder. Four decades on, however, many rank Plastic Ono Band alongside the best of The Beatles’ work. “[Plastic Ono Band] was just as important as Sgt. Pepper, in terms of being a milestone and in terms of the direction that John took after that,” Ono later told Rolling Stone. “The album characterized the direction we went in together, and because of that, a lot of people resented it. They were saying, ‘Please don’t let the dream be over. Let us keep on dreaming.’ They didn’t want to know.”