Master classes don’t get any more transformative than those led by the mezzo-soprano superstar Joyce DiDonato. At the pinnacle of her powers, she treats singers on the cusp as junior members of the guild, demanding the same intensity she demands of herself. Take nothing for granted. Don’t coast on voice. Never stop digging for the secret thoughts and moods behind each note, each word. Often, DiDonato will discombobulate a singer mid-aria with improvised backtalk from the silent scene partner the singer would be addressing onstage. Now, there’s a lesson, if ever there was one, for being in the moment. Which, when you come down to it, is the name of the game. In the hit play Master Class, which dramatizes historic sessions Maria Callas conducted at the Juilliard School in 1971, Terrence McNally has a discouraged “victim” whimper, “This is hard.” Duh! Callas can’t believe her ears. “‘This is hard!’,” she mocks. “Where am I?” But the ordeal continues. “It’s important?,” the victim pleads. “It’s life and death,” Callas replies, “like everything we do here.” —Matthew Gurewitsch