“The note,” Mr. Adès said, “the range, the tessitura, is a metaphor for the ability to transcend these psychological and invisible boundaries that have grown up around them.”

Adding to the excitement of the high A is its placement in the score. Unlike in other high-flying parts — the imperious Queen of the Night in “The Magic Flute,” the spunky Zerbinetta in “Ariadne auf Naxos,” the long-suffering title role in “Lucia di Lammermoor” — there’s little time for Ms. Luna to warm up: The A is her very first note, sung before she’s even visible onstage. (She sings it again a short time later, as the party guests, in a surreal portent, leave the stage and re-enter.)

“It’s a moment of arrival,” Mr. Adès said. “It had to be on this note.”

Growing up in Oregon, Ms. Luna sang the daunting Queen of the Night when she was still in high school “just because it was fun,” she said. “And I liked the sensation it made in my bones, in my head, in my sinuses. It just gave me a high. It still gives me a high.”