The word “diva” is bandied about too loosely these days. Things have reached the point where just about every competent pop vocalist with a good stylist and a bad temper thinks she deserves the appellation.

But, oh! there once was a time when diva meant something, when it was reserved for a world-renowned operatic soprano at the top of her game. And, of course, upon reaching the pinnacle of success, all the best divas got down to the business of suffering a tragic and scandalous decline.

In her time, Maria Callas was diva extraordinaire—La Divina, in fact. (During one performance of Aida, her interpolation of a high E-flat rocked the world; people still talk about it.) But the Callas in Terrence McNally’s Master Class is the post-decline Callas of the early 1970s when, years after having left the stage, she condescended to teach voice classes to terrified Juilliard grad students. These became a sensation and attracted admission-paying audiences.

In this production, we are cast as those admiring observers. Callas (Anne Cullimore Decker) breezes onstage and forbids applause—even as she visibly basks in our adoration, knowing that she had us at, “Hello.” Decker wields her formidable charm and magnetism like a laser, engaging the audience with breathtaking dexterity. She makes it look easy.

Vocal fireworks are provided courtesy of the supporting cast. There are strong and nuanced performances to be found here; it’s impressive to watch two sopranos (Natalie Blackman and Stefanie Londino) modulate their vocal techniques in response to Callas’ tutelage. And, as Tony the Tenor, Shane Haag offers a crackerjack “Recondita Armonia.”

Master Class @ Salt Lake Acting Company, 168 W. 500 North, 801-363-7522, through Nov. 8. SaltLakeActingCompany.org