Years ago, while talking to the late Cosimo Matassa [Tape Op #40], I remember marveling at the sounds he had achieved while recording early hits for Little Richard, Fats Domino, Roy Brown, and many others in the '40s, '50s, and beyond. Initially he was working with a limited number of tracks, a small microphone selection, and a mixer with a couple of channels. Yet he captured some amazing music and performances with this modest gear. In most cases, everything had to be happening on the floor as the song went down.
Once a song had been recorded, the "production" was finished.
Music recording, outside of a few wild, inventive folks like [the late] Les Paul [Tape Op #50], mostly continued in this fashion up into the '60s. Musicians and/or singers would gather and run the song down live while a balance engineer would submix through a console down to a few tracks, as needed. Many engineers didn't even understand what to do with 4-track and 8-track machines when they showed up. "What do we need extra tracks for?" Many others, especially visionary producers and artists like George Martin and The Beatles, saw multitracking as a way to open up new creative doors. Production moved into the realm of overdubs and reduction mixes, and layers were being added. But as Geoff Emerick [Tape Op #57] has famously noted, mixing Sgt. Pepper's… was easy, as it was almost all reduced down to four tracks of audio, and decisions had been made already. Production had occurred in the tracking with the reduction mixing and overdub passes (many times, of multiple instruments, to one audio track).
Once all the parts had been recorded, the main job of "production" was finished.
But as the '70s dawned and 16-track and 24-track tape decks became the norm, more control came into play. With drums, the engineer could now record kick, snare, et.al. to their own tracks on tape, and then apply changes to the sounds and levels later. Almost every instrument, voice, and overdub could have its own track on tape and channel, granting an unprecedented level of control at mixing.