[1] Other tracks on Apple Jam include musical contributions from Billy Preston, Klaus Voormann, Ginger Baker, Gary Wright and Bobby Keys.
According to bassist Klaus Voormann, a friend of the Beatles since their years in Hamburg and one of many musicians who played on George Harrison's All Things Must Pass album,[2] jamming was commonplace during the sessions and indicative of the free spirit that characterised the project.
[5][6] Harrison recalled that early in the All Things Must Pass sessions, he and his fellow musicians would improvise on an idea and then ask to hear the jam played back, only to discover that the engineer had failed to capture the performance on tape.
[11] Lasting eleven minutes, the jam is a blues instrumental;[11] in author Simon Leng's description, the improvisation is achieved through guitar riffs and "shifting dynamics" over a single-chord theme.
[13][17] Originally 20 minutes in length and referred to in Harrison's notes as "Jam (3)", it was recorded at EMI Studios on 2 July 1970,[18] the penultimate day of full band sessions for All Things Must Pass.
[12] Beatles historian Bruce Spizer highlights Harrison's guitar playing, the "rollicking" piano, and Keys' saxophone contribution, which he likens to the "jam ending" on the Rolling Stones' 1971 track "Can't You Hear Me Knocking".
[11][nb 2] "It's Johnny's Birthday" is a 49-second track sung to the tune of Cliff Richard's 1968 hit "Congratulations" and delivered in a style that author Ian Inglis terms "music hall sing-along".
[36][39] Whitlock recalls "Plug Me In" as an early example of him playing piano, the style of which he credits to Jerry Lee Lewis and Little Richard, as well as a rare contribution from Mason during the All Things Must Pass sessions.
[24] The main session took place at Olympic Sound Studios on 29 March 1969, shortly before Harrison started production on Preston's first Apple Records album, That's the Way God Planned It.
[48] In many countries, the Apple Jam sleeve was the only place where Clapton was listed as a musical contributor to All Things Must Pass, since rivalries between competing record companies prevented Harrison from acknowledging him in the main album credits.
[58] In music historian Dave Thompson's description, the record soon confirmed these journalists' speculation – namely that Harrison had long been stockpiling his songs, unable to include more than two compositions on each Beatles album, and that "he'd spent a lot longer jamming with his heavyweight friends than anyone could have guessed.
"[21] When preparing the 30th anniversary edition of All Things Must Pass in 2000, Harrison changed the order of the Apple Jam tracks so that "It's Johnny's Birthday" became the opener and "Out of the Blue" closed the album.
"[71] Less impressed with Harrison's religious stance in the main body of songs, Peter Reilly of Stereo Review wrote that "he seems freer and more involved" in the collaborative set-up reflected in the jam tracks.
[73] Don Heckman of The New York Times deemed All Things Must Pass a "blockbuster" and a major artistic statement by the former Beatle,[74] but said of Apple Jam: "Harrison playing guitar with such dynamite contemporaries as Eric Clapton and Dave Mason – nice, but not really a very exciting addition to the album.
[76] GQ's George Chesterton says that rock "never got more imperial" than on All Things Must Pass but he dismisses Apple Jam as "frankly forgettable", adding that its inclusion "rather illustrates the excesses of the record industry in 1970 and the baronial power of an ex-Beatle to do whatever the hell he wanted to".
[78] Roger Catlin of MusicHound and Tom Moon, in his entry for All Things Must Pass in 1,000 Recordings to Hear Before You Die, both view the jam disc as a complement to the high-quality, spiritual-themed songs on the first two LPs.
[81] Reviewing for AllMusic, Richie Unterberger describes the inclusion of Apple Jam as "a very significant flaw" but recognises that its content "proved to be of immense musical importance", with the formation of Derek and the Dominos.
[82][nb 7] AllMusic critic Bruce Eder similarly sees the third disc as "historically important as the sessions that spawned Eric Clapton's band Derek and the Dominos".