J.S. Bach composed his St. Matthew Passion in 1727. But for the better part of a century after that, the piece essentially disappeared, unknown to all but a few specialists. One of those specialists was the composer Carl Friedrich Zelter, who was the music teacher of a boy named Felix Mendelssohn. Mendelssohn was only about fourteen when his grandmother gave him a copy of the full score of the St. Matthew Passion – a score she had borrowed from Zelter…. The teenager immediately recognized the