John Lennon and Yoko Ono in New York just months before Lennon's murder on Dec. 8, 1980. Lennon would have turned 70 on Oct. 9 of this year. (Brenda Chase/Newsmakers)

John Lennon would have turned 70 on Oct. 9. Thanks to a series of Yoko Ono-approved events – special concerts, CD reissues, museum exhibits, a ceremony at the Imagine Peace Tower in Iceland – the occasion was hard to miss.

John Lennon's solo career contained several peaks, but nothing that matches the breathtaking sonic innovation of Strawberry Fields Forever or I Am the Walrus.

Of course, any talk of Lennon anniversaries leads to the bitter memory of his murder on Dec. 8, 1980, shortly after he turned 40. We know that a seismic musical force was lost, but it's impossible to gauge what Lennon might have achieved in the past 30 years. Would the senior citizen still be making music? Would he have weighed in against the U.S. military campaign in Iraq? Would he be sharing his thoughts via Twitter? Would he – God forbid – have done a duets album with Bono?

George Harrison once claimed that his former bandmate would have gladly joined The Traveling Wilburys, the late-'80s band that featured rock icons Harrison, Bob Dylan, Roy Orbison, Tom Petty and Electric Light Orchestra frontman Jeff Lynne. One can imagine Lennon salivating at the chance to play with Orbison, but the ex-Fab had openly derided Dylan's embrace of Christianity in the late '70s, which could have made things a bit thorny in the studio. And would he really have wanted to work alongside Beatle-wannabe Lynne?

It's tantalizing to consider the possibilities, given Lennon's towering genius and the fact that his solo career was so short – it lasted just over five years, when you take into account his self-imposed exile from the music biz between 1975 and 1980. In contrast, Lennon's longtime creative partner/rival, Paul McCartney, is still recording new material 40 years after the Beatles' breakup.

The cover of the 1980 album Double Fantasy. (Capitol)

Lennon's solo career contains several peaks, but nothing that matches the breathtaking sonic innovation of Strawberry Fields Forever or I Am the Walrus. Beatles producer George Martin once observed, "John and Paul were equal talents who collaborated but, more important, who competed. When one guy did something, the other would say, 'My God, that's good. I wonder if I can do better?' That spurred them on. They were great individually, but they never quite reached the Olympian heights that they achieved when they were the Beatles."

Neither Lennon nor McCartney ever found a collaborator that could inspire them in quite the same way. Lennon partnered briefly (and effectively) with Elton John (on the single Whatever Gets You Thru the Night) and David Bowie (Fame), but those unions didn't last. Yoko Ono was of course Lennon's long-time muse and bed-in partner, but she hardly possessed McCartney's melodic gifts.

While the master craftsman McCartney has chugged along without serious interruption – specializing in sunny pop confections, while making occasional forays into electronica and classical music – Lennon became disenchanted with the business. He made fewer concessions to the marketplace than his ex-partner, seeking instead to bare his soul – relentlessly – through autobiographical songs.

Tracks like Mother (from John Lennon/Plastic Ono Band, 1970), Jealous Guy (Imagine, 1971) and Steel and Glass (Walls and Bridges, 1974) are masterpieces of emotional vulnerability, each featuring a gorgeous melody and a heart-wrenching Lennon vocal. But Lennon could also seem lost, creatively. On the largely forgotten Some Time in New York City (1972), he forsakes poetry for simplistic sloganeering, while Mind Games (1973) and his 1950s oldies album, Rock 'n' Roll (1975), are curiously uninspired. After dealing with the personal betrayals and financial complexities of the extended Beatles breakup, various lawsuits and a period of marital discord, Lennon needed a break.

So where was he heading musically at the end of his life? After his five-year hiatus, Lennon returned in November of 1980 with Double Fantasy, a collaboration with Yoko. (Subtitled A Heart Play, husband and wife each performed seven songs on the album.) John's contributions – including Woman, Watching the Wheels and Beautiful Boy (Darling Boy) – are pleasant and tuneful odes to domestic bliss, but less adventurous and energetic than his wife's efforts. On songs like Kiss Kiss Kiss, Yoko's sound was in sync with the then-prevalent "new wave," while Lennon seemed to be moving backwards in time, channelling Elvis Presley and Roy Orbison on (Just Like) Starting Over.

The immediate reaction to Double Fantasy was mixed. "The time spent in seclusion and semi-retirement appears to have dulled the man's sensibilities," observed the British music paper Melody Maker. "It's a godawful yawn." That's probably an over-reaction from a publication besotted with punk and Adam and the Ants, but there was a palpable sense of anti-climax in the critical response to John's mid-tempo ballads.

I remember the great anticipation surrounding the album's release – five years had felt like an eternity, and like many music fans, I waited with bated breath to hear Lennon's pronouncements on the intervening half-decade. It was great to have him back, but the fact that the social campaigner was relying so heavily on his blissed-out family situation for lyrical inspiration threw many of us for a loop.

At the time of Lennon's death, Double Fantasy was at No. 11 on the U.S. album charts and at No. 46 in the U.K. After his death, it rose to No. 1 in the U.S. and No. 2 in his native land.

Thirty years later, the album still sounds as if Lennon was taking tentative first steps back into the world of commercial music making. One can't help but think that his material would have once again become edgier as time passed. Surely he would have shifted his creative focus outside the four walls of his apartment in Manhattan's Dakota building, where he lived with Yoko and son Sean. On the last night of his life, Lennon was at the Hit Factory recording studio in New York, adding some scorching guitar riffs to Yoko's dance track Walking on Thin Ice. It was more vibrant and kinetic than anything on Double Fantasy.

Amid all the conjecture about his future musical plans, one thing is certain – Lennon had planned to do a tour in 1981. On Dec. 8, 1980, that plan changed – horribly, unexpectedly, irrevocably.

Greig Dymond writes about the arts for CBC News.