This thread brings back memories. I hope everyone will read the old thread that I contributed to:
I pretty much covered the subject there, but I would like to elaborate, mostly for Chronos.
I’ve been out of professional music for a few decades, so things might have changed. But, in my experience, there is often a wide gap in the capabilities and desires of born-on-the-bayou musicians, who rarely read or write any music other than a crude chord chart, and studio “session” musicians. These typically are string players, who often come from a formal, classical background and can read music better than anyone. Time is money, and musicians who can bash out 3 recordings in a single 3-hour session are the best bargain for producers, so sight-reading music is a must.
I often attended recording sessions where the strings saw the music for the first time, and could lay down a decent final recording of a song in the few minutes left in a union session, on the first run-thru. This avoided having to pay them overtime, or kick some other group off the studio’s time chart, something that nobody wants to do.
BTW, “sweetening” charts or sessions are used to add more orchestral tracks, typically strings or horns, on top of a basic band’s original recording. It is typical that an arranger is called in after the basic – mostly rhythm sections and possibly a scratch vocal – are done. This arranger is in the class of musicians who can read music, since that is how the arranger communicates with the performing musicians, although typically the arranger attends and conducts the orchestra for the studio takes.
When a rock band plays/records a new song, sweetening tracks may be planned, but not mapped out in detail yet, this being done much later.
So, to sum up, not all commercial/professional musicians read or write music well, but some do.