Being in the choir and doing these challenging pieces has made me realize what an intellectual effort it is. It's clear that most others in the choir have done these pieces before. They are sailing along, while I'm concentrating on every note.

When we get it together, the results are glorious - beautiful, energized and complex. But that complexity demands that the music be right, be regular, be clear - in fact, that it follow rigid rules.

Every time I come to that wrong expression, I get a sensation as if a small area of my gray matter, say 1 teaspoon of it, is shrinking in on itself, fighting off the input. That interferes with my concentration on the sound.

I have a friend who is a very talented pianist. She can sit down and read off the most complicated music you can imagine. But when an amateur composer gave her a hand-written MS, she couldn't deal with it. She depends on neatness, precision, straight lines - in a word, on geometry to read music. It's a similar thing.