With all due respect to the folks who are going to immediately decide I have said something non-positive about the Beatles and respond defensively, what do we know about the provenance of this recording? Specifically is the audio live and unprocessed in any way or has an original recording been cleaned up and enhanced in some way? I do not doubt that the Beatles could have nailed the harmonies under adverse conditions since even I personally have gotten lucky and done that occasionally. My question is merely whether this is an unadulterated example of that?
Two examples of why I ask are because we have discovered that many of the famous performances on broadcast TV of the 60's were merely lip synching. There were some genuine live recordings and the detective work to figure out which ones are which is interesting. Several songs on Zappa recordings from the 70's sound like they are live, in concert, but the album release was sliced together from the best parts of multiple concerts. (Roxy Live and Elsewhere comes immediately to mind since I know people will react to the mention of Frank ;-) )
In the days of "live TV", lip syncing a tv performance was commonplace for everyone. This Beatles performance is not the case. All the audio/video 100% matches up.
The original audio source has undoubtedly been enhanced, but the actual performance itself is 100% original and hasn't been tampered with. I can assure you of this. On one of my external hard drives full of live music, I have a folder containing 12gb worth of live Beatles recordings...pretty much every live Beatles recording known to exist. (and 12 GB is a LOT considering their typical early shows came in under a 1/2 hour in length!) One recording after another shows them consistently nailing their harmonies despite their hardly being able to hear themselves, much less one another. Some shows are more rushed than others, and they vary greatly in recording quality, but on the whole, they always performed very well and never had any serious flubs.
As for Zappa, it is pretty well known to fans/collectors that as soon as 16 track recorders were mobile enough to take on tour, he'd record entire tours, having his band play to a click track solely for the purpose of being able to mix and match individual tracks from various night's performances, and Frank was very open about it. IMO this in no way detracts from the legitimacy of their being authentic "performance recordings". Even Led Zeppelin's live album How The West Was Won (from Long Beach and LA 72 tour) contains a lone dubbed in organ track on the song Thank You from their Southampton University multitrack recording from 73 as the original mellotron track was way out of tune.
If you want examples of real doctored live albums, go no further than Kiss Alive, which is basically drums, some bass, and crowd noise w/ all vocals and guitar being rerecorded in a studio. Or Judias Priest' Unleashed In The East where all vocals were overdubbed in a studio. Or James Brown, where most of his live albums contain some tracks recorded entirely in studio w/ added reverb and audience noise dubbed on top.