In the last summer of his life, Mozart wrote a piece barely three minutes long — and poured more peace into it than most composers manage in a lifetime. This is Ave Verum Corpus, K. 618, composed in June 1791. Mozart was 35 and had less than six months to live. He wrote it almost as a favor: for Anton Stoll, a choirmaster in the small spa town of Baden, where Mozart's pregnant wife Constanze was staying to take the waters. It was meant for the feast of Corpus Christi, a modest occasion, for a mo