When performing from score, I did what I could to focus before playing, but, because playing from score didn't force all of the good habits I've been writing about, I wasn't as concerned with some very basic issues. Believe it or not, those basic issues included optimal tempo, listening to the room, and hearing a piece before playing it. Indeed, I had gotten quite used to just diving into a piece. After all, I had the score to save me from any major accidents.
For me, the score was a barrier to the music. I don't just mean this metaphysically; I mean it in the most concrete terms. I couldn't hear the instrument as well, and in turn, I wasn't listening to the way the music was sounding in the room. Ultimately, this meant that I wasn't listening to the music.
Imagine: week after week of practice with a score in front of my nose, regularly not hearing the instrument at its best. No matter what you think about memorizing music, you certainly must agree that this is an aural impediment!
(Obviously, I'm writing here specifically to keyboardists, whose scores block direct sound from the vibrating strings. But doesn't a baffle (i.e., a score) in front of other instruments affect the way the sound enters the room? A 'cello, a flute, a violin, a voice? I think so.)
Today, I think before I play. I settle down before the keyboard, and I envision the opening measures of what I'm about to play. I breathe, I calm myself. I pay close attention to finding my starting tempo. I recall my meditation practice in order to be totally present.
For this reason, I think twice before agreeing to a lecture recital. It's very hard to settle into a state of total presence when I'm wondering, "What did I just say?" or "What should I say?" A lot of presenters ask if I would talk about pieces before I play them. I only do this if I'm really comfortable with a program, and I strongly discourage it for anyone who's just becoming comfortable with playing by heart.
Don't forget: presenters don't often have your best interest in mind. You can easily talk them down by saying that, as a memorizing musician, you need to stay focused. If they don't like it, they can hire the guy who needs a page turner.