India, Aug. 24 -- There is a frightening moment in choral singing when the entire choir begins to lose pitch.

Nobody notices it at first.

The sopranos are singing confidently. The altos are following the sopranos. The tenors are following the altos. And basses, being naturally humble people, are following everybody while looking as if everybody is following us.

The strange thing is that we all sound correct to one another.

We are united. We are disciplined. We are singing the same song. We may even be smiling proudly at the audience.

Unfortunately, we are all wrong.

This happens especially when a choir sings without accompaniment. Slowly, almost politely, the pitch begins to slip. One voice moves slightly. Another adjusts to it. A ...