Back in the day I worked with a well known goth band, and for each song on the album it was pretty much this:
1) Tape machine = 48 track analogue. 2 x 2" tapes 24 tracks each. Master and Slave.
2) Each song one master tape (24 track) and multiple slave reels (24 track) which would sync up with the master.
2) On one master tape Drums and bits/bobs, guides.
3) One slave reel of lead vocals to be bounced down to two tracks onto the master.
4) One slave reel of BV to be bounced down to a few BV tracks onto the master.
5) One slave reel of bass to be bounced down to one or two bass tracks onto the master.
etc... etc... You get the idea.
Each slave reel was listened to a few bars at a time and given a score and written down on a grid on a piece of paper. From that the best performances could be determined. If the best performance didn't gel with something then we went down to the second best performance etc. All ended up being bounced onto the master. We had other slaves that ended up on the final mix like large choirs etc.
We even got into scoring mixes, not surprising it took forever, and artist had the habit of disappearing for days on end. At one stage record company came in to claim the master tapes (the costs must have been enormous) but we were one step ahead. Eventually we got there and artist got exactly what they wanted, and it was a big enough hit for the record company to get their money back I suspect.
All on analogue tape. Think what could have happened with takelanes in Sonar...
Rock and roll....