John Lennon/Plastic Ono Band, John Lennon. Apple, 1970.

THE 1970s DAWNED with a blistering hangover. On September 13, 1969, just before Abbey Road began dominating end-of-’60s radio, John Lennon sang at the Toronto Rock and Roll Revival, an early 1950s festival. He called his pickup group the Plastic Ono Band: Eric Clapton (lead guitar), Klaus Voorman (bass) and Alan White (drums). They launched with standards, “Blue Suede Shoes, “Money,” and then “Dizzy Miss Lizzy,” before turning to Lennon’s “Yer Blues,” an unreleased “Cold Turkey,” and “Give Peace a Chance,” his anti-war chant. Then he turned the stage over to his Japanese-American wife, Yoko Ono, who screamed against Lennon’s guitar feedback for almost half an hour. It stupefied the audience. One week later, at an Apple business meeting in London, Lennon told the other Beatles he wanted a “divorce.” However, Lennon agreed to keep a lid on his departure—they were in the middle of contract negotiations, and if word got out, they could lose leverage. From that point on, the chronology went extremely fuzzy for most fans, as Beatles group releases overlapped with the members’ early solo records. Plans progressed for a Let It Be album and film early in 1970 (shot in January 1969) as the breakup remained a secret...