Video: 'It's So Hard (Evolution Documentary)'

(Monday, July 5, 1971) — Former Beatle John Lennon completed five tracks for Imagine, his second studio album, today at Record Plant East at 321 W. 44th Street in New York City, overdubbing saxophone (performed by King Curtis) to “It’s So Hard” and “I Don’t Wanna Be a Soldier Mama.”

Video: 'It's So Hard (Remastered 2010)'

The sessions captured some Curtis’ final performances as he was murdered shortly before Imagine was released.

Video: 'It's So Hard (Ultimate Mix)'

Curtis, 37, was stabbed on Aug. 13, 1971, during an argument with a pair of drug dealers. He was discovered on the steps outside his Manhattan apartment at 50 West 86th Street.

Curtis was attempting to carry an air conditioner into his apartment when a man named Juan Montanez refused to move from the entrance. A fight ensued and Montanez stabbed Curtis. Curtis was transferred to Roosevelt Hospital, where he died.

Curtis was declared dead in the same in the same emergency room that would declare Lennon, 40, dead after he was shot in front his apartment building, directly 14 blocks south of Curtis’ 1971 apartment building, by a deranged fan nine years later in 1980.

Video: 'I Don’t Wanna Be A Soldier Mama I Don’t Wanna Die (Evolution Documentary)'

Video: 'I Don't Wanna Be A Soldier Mama (Remastered 2010)'

Video: 'I Don’t Wanna Be A Soldier Mama I Don’t Wanna Die (Ultimate Mix)'

Also today, Lennon’s “God Save Us” and “Do the Oz,” written and recorded in support of the defence fund during Oz magazine’s obscenity trial, was released as a single in the U.S. (July 16, 1971 in the UK).

Video: 'God Save Us (Ultimate Mix)' (lead vocal by Bill Elliot was overdubbed June 9, 1971)

Lennon’s vocal for “God Save Us” was replaced by Bill Elliot on June 9, 1971, at EMI Studios in London with Mal Evans at the controls following the Lennons’ June 1, 1971, departure for a six-week stay in the United States, and credited to Bill Elliot & The Elastic Oz Band.

Video: 'Do The Oz (Ultimate Mix)'