Sorry, but once I get on a roll, I can’t stop…so, to partially address the OP…
Modern recorded music is done two ways. Either the entire song is recorded at once, with all musicians playing simultaneously (like a “live” recording), or in layers, where a basic track is augmented by additional instruments and tracks repeatedly until the final result is achieved.
Until the advent of multi-track recording, the layered approach was impossible or difficult, but with digital techniques, there is almost an unlimited number of tracks that can be added or subtracted, remixed or enhanced. Sometimes these tracks are recorded (simultaneously or sequentially) in different places, in different countries, at different times.
How does a producer decide which method to use? Depends. With the all-at-once method, the cost is for personnel and space (it costs more to hire a 100 piece orchestra than a 4-piece rhythm section). With the layered approach, the cost is time. If the performing group is doing their own recording, or working as royalty artists, their time may be essentially volunteered, not on the clock.
I have attended or been part of, both kinds. I once worked for Barbra Streisand, who liked to record with an entire orchestra at once (she could afford it). She hired an arranger and worked closely with him, privately, on the complete master score, and we went into a huge scoring stage studio at Warner Brothers to record. After some rehearsal, Barbra went into the isolation booth to record a scratch vocal simultaneously with the orchestra.
The only layering done here (at a subsequent session) was to improve and enhance the original master orchestral recording by replacing the scratch vocal with a more polished one.
The advantage of this all-at-once technique is you have a finished product almost instantly.
In contrast, many Beach Boys recordings, like Good Vibrations, were layered many times and different ways over months, as this was the way Brian Wilson liked to work.
So the answer to “who scores modern music?” is it depends.