John Lennon wasn't exactly feeling the post-Beatles blues in 1971, but his first few solo albums fell short of his band's commercial achievements. Then again, it's not like the experimental works he made with Yoko OnoUnfinished Music No. 1: Two Virgins, Unfinished Music No. 2: Life With the Lions and Wedding Album – were aiming for chart dominance.

But his first real solo LP, 1970's John Lennon/Plastic Ono Band, released eight months after the breakup of the Beatles, was a personal, complicated project, and one whose primal-scream approach and bitter lyrics were a bit off-putting to casual music fans. The album stalled at No. 6 on the chart, a position not even the worst-performing original Beatles albums – like Yellow Submarine, which included only four previously unreleased band songs – even approached. (That 1969 soundtrack, like a handful of other Beatles underachievers, peaked at No. 2.)

Paul McCartney's debut solo album made it to No. 1. So did George Harrison's first proper one. (Ringo Starr had to settle for a No. 22 showing for his first record without the Beatles.) Point is, the man who led the Beatles during their first couple of years wasn't the big-time solo artist his bandmates were now that everyone was on his own.

That all changed with Imagine, which was released on Sept. 9, 1971, in the U.S. (It came out a month later in the U.K.) Imagine became Lennon's first No. 1 album as a solo artist. But more important, it allowed him to reclaim his legacy with a record that, by toning down Plastic Ono Band's abrasiveness, sounded more like the Lennon fans fell in love with in the '60s.

It's not that Lennon wasn't in a typically feisty and fighting mood. "How Do You Sleep?" was a dig at McCartney. "I Don't Wanna Be a Soldier" shot down society's prescribed roles. And the classic title track was, among other things, an anti-religion proposal partly disguised as an idealistic peace anthem.

Watch John Lennon's Video for 'Imagine'

But compared to Plastic Ono Band's stripped-down and aggressive arrangements and delivery, Imagine sounded like a peaceful and pop-leaning respite from the confrontation that dominated Lennon's past couple years.

The album's sessions were recorded during a couple of different periods: first for two days in February 1971, at the same time as the "Power to the People" single, and later, with more commitment from producer Phil Spector and a backing band that included Harrison as well as members of Badfinger and future Yes drummer Alan White, in June and July, when the bulk of the tracks was laid down.

Reflecting the spirit of the era, as well as Lennon's creative restlessness, Imagine pulled its songs from several sources. In addition to the McCartney slam "How Do You Sleep?" ("The sound you make is muzak to my ears," he sings), songs originated from Lennon's primal therapy ("Oh My Love," "How?"), his marriage ("Oh Yoko!") and even his Beatles days (both "Jealous Guy" and "Gimme Some Truth" were written and originally recorded during sessions with his old group).

But Lennon coated the tracks in a sweetness that was missing from Plastic Ono Band. It did the trick, sending the album to the top of the charts and on its way to becoming his best-selling solo record. Lennon often complained that the honeyed production concealed the political nature of some of the songs, especially the title track, a No. 3 hit. Still, it proved he could be a solo star like former bandmates McCartney and Harrison, both commercially soaring since the breakup of the Beatles.

In the years since its release, and Lennon's death, the album's stature has grown along with the massive popularity of the title song, whose message – as Lennon himself noted – was often lost on the people who praised it. He called it "anti-religious, anti-nationalistic, anti-conventional, anti-capitalistic." In other words, it was everything Lennon stood for. And it sums up his most enduring solo album.

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