For those who can't be bothered to watch the documentary

 

Watched a thing with Peter Jackson being interviewed, he was saying about the way they had to deal with the audio, that the mics to pick up speech were struggling with the music playing, but then his team “invented” a demixing software to be able to extract the instruments and voices, as the stuff that is out there commercial wouldn’t do it. He said you had Ringo banging away and it would isolate the other stuff like it was in another room.

I wonder if that software will see the light of day? I know it’s a relatively straightforward mix, and they also had the elements recorded to tape that they could use to subtract, but would be interesting to see how they pulled it off.