“There was resistance,” María Victoria Alcaráz, the theater’s director, said in an interview. “At institutions as old and traditional as the Colón Theater, there’s a tendency to do things the way they’ve always been done.”

Getting the theater to budge took years of dogged training, an extraordinary vocal range and a showstopping performance last year that turbocharged Ms. Castillo’s career — turning an accomplished lyrical singer into a breakout star who has shaken up the staid opera scene.

From her background, Ms. Castillo, 34, would seem to have been an unlikely opera star. But she pursued her dream from an early age.

She was born in a small town outside São Paulo to a Brazilian mother who made a living cleaning wealthy people’s houses and an Argentine father who worked in construction. During her childhood, the family toggled between the two countries as work opportunities came and went.

“It was an austere childhood but I never lacked anything, and my parents always made sure we had the essentials: education and food,” said Ms. Castillo, the oldest of three children. “They made it clear that to get ahead, we needed to study.”