Did you ever wonder how the parts get prepared for all orchestral and opera performances?
Well someone has to do that. And he or she is called a Music Librarian.
Even before the first rehearsal, parts have to be ordered, marked with cuts, bowings, expression marks, etc., so that the chorus and orchestra can follow the same guidelines. The person who does that job, is called a 'music librarian.'
This job is often split in an opera company such as ours, between the Music Department -- in our case headed by Associate Artistic Director and Conductor Joe Walsh, who orders the edition and the parts and then discusses and identifies and distributes the cuts, and also in his case prepares all the preliminary chorus parts with diction and translation markings for the first rehearsal, --- and the Symphony librarian, who is hired to place the cuts, bowings, and important markings into the orchestral parts which will be rehearsed and performed by our two orchestras depending upon the opera -- the Virginia Symphony or the Richmond Symphony.
I think this article by the Seattle Opera Music Librarian will give you a good view of what needs to happen before even the first rehearsal.
Click here to read it.