The material for Mozart’s azione sacra is taken from the Old Testament book of Judith, the story of the beautiful Israelite who steals into the enemy camp of the Assyrians and decapitates their sleeping commander, Holofernes .

Often called a stroke of genius by the fifteen-year-old Mozart, Betulia liberata brooks comparison with his early operas in every respect. But Mozart was evidently concerned to distinguish between an azione sacra and an azione teatrale in the music itself, e.g. in the a...