Bach's St. Matthew Passion is universally acknowledged to be one of the world's supreme musical masterpieces, yet in the years after Bach's death it was forgotten by all but a small number of his pupils and admirers. The public rediscovered it in 1829, when Felix Mendelssohn conducted the work before a glittering audience of Berlin artists and intellectuals, Prussian royals, and civic notables. The concert soon became the stuff of legend, sparking...