If Mozart’s widow, Constanza, is to be believed, the happiest days of Mozart’s life occurred in 1780, when he was 24 years old and writing the music for “Idomeneo,” an opera that had its premiere performance in Munich on today’s date in 1781.

Mozart had good reason to be happy. For starters, the best orchestra in Europe, the Mannheim Court Orchestra, had relocated to Munich, and that orchestra would be the pit band for his new opera. The lead role was being written for Anton Raff, a famous tenor of his day, and, even better than that, there were some exceptionally talented—and exceptionally good-looking—young sopranos in the cast as well. Mozart promptly fell in love with one of them, a strikingly beautiful diva named Aloysia Weber, but ended up marrying her sister Constanza instead. By contemporary accounts, Aloysia, with her high cheekbones and magnificent carriage, was close to the ideal beauty of the day. But Mozart came to appreciate Constanza’s more sympathetic personality, not to mention, in his own words, her “two little black eyes and pretty figure.”

Mozart had written several operas already, but music historians are right when they say the canon of truly great Mozart operas begins with “Idomeneo,” an opera that must have been, literally and figuratively, a labor of love.