I love that Apple have now set the precedent of going back to the pre bounce session tapes for remixes. They first did it for the "Yellow Submarine Songtrack" CD, which was the stereo mix companion of the 5.1 mixes done for the remastered version of the film. But since that was for the film and not an "official canon" album all of us Beatle hardcores didn't know if they'd dive in with a full on remix program. The remixes for the "1+" album in 2015, again done the same way with first generation pre-bounce session tapes, were just another indicator they were serious about doing this on a large scale, on the albums themselves.
Half of me feels that too much Lucasian futzing with the albums is almost heresy but all the original mixes are still there, remastered beautifully in 2009, and the fact Giles Martin is the custodian of this remixing endeavor I feel like it is okay with the Universe... plus Paul, Ringo, Olivia & Yoko all have signed off on it.
The only problems that would've given Giles some headaches & head scratchers is that the Beatles often, using today's parlance, "pre produced" (i.e. thought ahead) their recording process knowing the limitations of 4 track. Meaning: on the first 4 track session tape they might record drums & bass on 1 track together, with guitars & piano on another, etc. Recording more parts together to avoid multiple bounces was to avoid too many "reduction mixes" as EMI termed them, especially in the early albums when the band played most rhythm tracks live as a band. A song during the era after "Please Please Me" two track recording & before the experimentation of 1966 would be the four main instruments on 2 tracks and the other two would be for vocals & solos. Song's did not go into many reduction mixes if at all.
It is unclear if the Beatles still utilized these methods on Pepper for every track, but as the bonus material shows, a track like "Fixing A Hole" had a basic live rhythm track of harpsichord, drums bass, McCartney's vocal etc. Did each of those instruments get their own track
or did they still use techniques they'd used for at that point years? Where isolation of every element wasn't possible is difficult to suss out even with Mark Lewisohn's Recording Sessions book as a guide it's not possible to suss out.
Giles would also lose complete isolation of every soubd if the Beatles did any additional overdubs WHILE a 4 track to 4 track bounce was happening (an old technique those of us who started recording when "home recording" was still PortaStudio's can attest to using to squeeze every possible inch of space out of the 4 track limitation. Either way it's a fascinating process, and now that everything the band ever recorded that exists on tape at Abbey Road has been archived to 192kh/24bit who knows what projects could get greenlit.
I have demos from the Tascam 424 & 488mkII that I'd love to transfer to DAW but without a 4 input interface (my Tascam US-2X2 has only 2) and the logistical nightmare of getting 8 tracks of tape output from the 488mkII I have never done it. The syncing used on this landmark albums remix could probably be approximated with a decent DAW, but my concern of even just transferring the 4 track session tape twice (track 1 & 2 in one pass, then 3 & 4) is how wow & flutter or any miniscule tape speed fluctuations may sound. Eventually I will do it, even as an experiment on a song or two.
But rumors are already swirling that a 50th anniversary "White Album" remix has already been completed, and even though "Abbey Road" was recorded on 8 track I can see Giles & Apple wanting to remix it too. Again, I am if two minds, but the original mix sessions his Dad & Geoff Emerick and occasionally the Beatles did are still there on the shelf. For no matter how cool these remix projects are for analog recording & Beatles freaks like me the original mixes will always be the definitive versions.