Concerts by the Choral Society of the Hamptons are sources of pleasure for our audiences, and they receive wonderful reviews. But for me, the Choral Society is more than that: It is a personal delight — and a good cause. I sometimes call myself a defrocked soprano, because I once had all those top notes, but now am an alto. No matter. I can head into a rehearsal feeling tired or out of sorts, and it falls away as I concentrate on the score in my hands and the collective sound of music-making. “Zen and the Art of Singing?”