Based on a 1977 demo recorded by John Lennon in New York, Free As A Bird was completed by the other three Beatles 17 years later and released as the lead single from the Anthology project.
Yoko Ono provided the tapes that also included rough early versions of “Real Love” (which they later completed), “Grow Old Along With Me” and “Now and Then” (which they passed on). Sources: Beatlesbible.com – Ultimateclassicrock
In subsequent years the Anthology project slowly gathered pace, and by the early 1990s Paul McCartney, George Harrison and Ringo Starr were considering recording some incidental music as a trio. This idea was discarded in favour of new songs, but agreed that they could only reunite musically as The Beatles if Lennon was on the recording.
We took the easy route, which was to do some incidental music, because what else can we do? There were four Beatles and there are only three of us left. We were going to do some incidental music and just get there and play the instruments and see what happened. Then we thought, well, why don’t we do some new music? And then we always hit the wall, and OK, Paul had a song, or George had a song, or I had a song, well that’s the three of us, why don’t the three of us go in and do this. And we kept hitting that wall because this is the Beatles; it’s not Paul, George, and Ringo.
George Harrison and Neil Aspinall are believed to have made the initial approach to Yoko Ono, suggesting that the remaining Beatles add new instrumentation to unfinished recordings by Lennon.
On 19 January 1994 Ono met McCartney in New York, for Lennon’s posthumous induction into the Rock ‘n’ Roll Hall of Fame. McCartney presented the award, which was accepted by Ono on Lennon’s behalf.
That night Ono gave him cassette tapes containing four songs: Free As A Bird, Real Love, Grow Old With Me and Now And Then. The occasion marked a reconciliation between the pair, whose relationship had often been tainted by animosity over the years.
Although touched by the songs, McCartney was initially wary about adding to them.
I’d never heard them before but she explained that they’re quite well known to Lennon fans as bootlegs. I said to Yoko, ‘Don’t impose too many conditions on us, it’s really difficult to do this, spiritually. We don’t know, we may hate each other after two hours in the studio and just walk out. So don’t put any conditions, it’s tough enough. If it doesn’t work out, you can veto it.’ When I told George and Ringo I’d agreed to that they were going, ‘What? What if we love it?’ It didn’t come to that, luckily.
As perhaps expected, old tensions arose. McCartney and Harrison – in a repeat of an argument laid bare during the Let It Be film – disagreed over the guitar solo.
“I felt that the song shouldn’t be pulled in any way,” McCartney says in Still the Greatest. “It should stay very Beatles. It shouldn’t get to sound like me solo or George solo, or Ringo for that matter. It should sound like a Beatles song. So, the suggestion was made that George might play a simple, bluesy lick – rather than get too melodic.”
Lennon recorded “Free as a Bird” using a portable tape recorder with a small mic on top of his piano, which meant his vocal and accompaniment couldn’t be separated – only cleaned up. The demo also had to be edited because a relaxed Lennon wasn’t keeping steady time.
Lynne edited the song to smooth out the tempo, but the others still had misgivings. “At the beginning, it was very hard, knowing that we were going in there to do this track with [John],” Starr says in Still the Greatest: The Essential Songs of the Beatles Solo Careers. “It was pretty emotional. He wasn’t there.”
Starr reportedly used his original Ludwig drum kit on the sessions, while Lynne doubled McCartney’s piano with Lennon’s original turn, bolstering the sound.