Even more, googling, I get about 100k working musicians currently in the US. It should be obvious that most of those aren't hit-producers for major labels and things likely weren't that different back in the 1960s. Back in the day, they were live performers, teachers and performers in radio-orchestras. Presently they are live performers, teachers, session musicians , and composers-of-themes for movie, TV-shows, commercials, video games and so-forth.
Even more, googling, I get about 100k working musicians currently in the US. It should be obvious that most of those aren't hit-producers for major labels and things likely weren't that different back in the 1960s. Back in the day, they were live performers, teachers and performers in radio-orchestras. Presently they are live performers, teachers, session musicians , and composers-of-themes for movie, TV-shows, commercials, video games and so-forth.