The mood shifts for the lively opening scene, in which the Mother (Briana Hunter, a radiant mezzo-soprano), who is several months pregnant, talks with three girlfriends (Ariana Wehr, Brea Renetta Marshall and Mia Athey) about the husband she loves and the hopes she has for her child. In rapturous yet playful lines, she sings about her man: the bigness of his frame and smile; his head “full of big ideas”; his voice.

“I could pitch a tent and live in the body of that voice,” she sings. The music shifts from jaunty exchanges between the women to passages where the Mother’s fantasy of her family’s future is evoked by plangent, wide-spaced, Copland-esque chords.

The friends gently mock her infatuation. They’re alarmed, however, to learn that her husband is a police officer. “You married a cop?” they ask. And while they try to be supportive, they turn fretful when the Mother says the baby she is bearing is a boy. Nothing but trouble, her friends predict, only half-joking. The Mother asserts that she will keep her boy close and doesn’t care who he ends up being.

In impassioned moments like this, the characters sing soaring vocal lines cushioned by the orchestra. But just when you fear Ms. Tesori is pushing into melodramatic excess, she shifts the mood and surprises you.

The next scene takes place in the hospital after the birth of the boy. The Father (Kenneth Kellogg, a tall, commanding bass) has just seen the boy in a room where everything was white — walls, floors, sheets, nurses. Our “little baby boy,” he sings, was “like a black exclamation point on white linen paper.” He holds his son and vows to protect him.

The Father then visits three fellow black police officers watching a football game at a Harlem bar. “You got a son on the first try,” they say, envious, while kidding him over his burgeoning responsibilities.