To the Editor: I was driving along a sun-dappled road. The full panoply of nature's new greens exploded before me. From the radio came one of Mozart's gifts to the spirit. It was the kind of day that makes you count your blessings.Suddenly, there was a subliminal tampering with my psyche: the music changed. Half a dozen bopping sounds warned me that danger lurked, and a man's moonsilver voice — signifying that what he was saying was for my own good — told me that, at any moment, my heart might — more bopping — STOP! But, he says, . . .