On May 1, 1786, audiences at Vienna’s Burgtheater witness the premiere of "The Marriage of Figaro," Wolfgang Amadeus Mozart’s lively comic opera. Based on a once-controversial French play that poked fun at the upper class, the work mixed humor, romance and sharp social commentary. Though its initial critical reception in Vienna was mixed, the opera—widely seen as the first to bring emotional depth to a farce—soon won wider acclaim. It remains one of the most beloved operas ever written. By 1786, Mozart—just 30 years old—was already one of Europe's most accomplished composers, with dozens of now-canonical symphonies, concertos, sonatas, chamber works and sacred pieces to his name. He had also written more than a dozen operas, though not yet the works for which he is best known today. In the last five years of his life, before his death in 1791, Mozart produced a remarkable run of operas that remain central to the repertory.…