In my opinion, the music in front of you becomes a crutch. You know that music. You can sing it without the printed music in front of you.
This is the article by Scott Dorsey including a video with all the musicians including the conductor having memorized the music.
Date: June 15, 2012
Did you know that it takes exactly thirteen hours to memorize a piece of music? Yup! Twelve hours to complain about it and one hour to get the job done.
Of course, I’m being glib. Depending upon the complexity of the work at hand, memorization can be almost instantaneous, or it can present significant challenges. It stands to reason that the latter is the case here in this performance of Bach from a recent ACDA divisional conference.
What are some of the benefits of having singers memorize a work? Improved posture, better sound (choir folders make great baffles), and continual visual connection between the conductor and the choir are just the three most obvious answers. Are there risks? Yes, there are; a singer having a memory slip in an intricate work (such as the music of Bach), could bring the whole thing to a halt.
As an aside: note in this performance that not only are the singers performing without a score, but our colleague also took pains to memorize the work. What are the benefits to the conductor who has the score memorized? Since it's summer, why not start memorizing your scores right now?
I would love to hear what you think. Now, in the piece above we aren't going to notice as much if a word has been missed or are we?