Do you want an oboe player who has a dry sound or someone with a warm sound? Do you want the trumpet to be high and screeching like in, say, “City of Angels,” or more symphonic like in “Les Miserables?” A violin sound that’s light on the vibrato or something bold and bravura?
This is from an article about a New York music contractor. It’s a fun little read.
I’m fortunate. I play in orchestras with tenure, and I rarely do freelance work. I can tell you, from past experience, that the freelance life is stressful and difficult. You never know when you’ll be deleted from a list. The rights of a freelancer are minimal.