AUSTIN, Tex. — Holding his whiskey in one hand and his Stetson in the other, the opera’s hero — a tough stagecoach driver — offered an unhappy barmaid some advice in a strong, clear tenor voice.

“You could be anything,” sang the tenor, Holden Madagame.

He should know. Mr. Madagame, 28, is part of a new wave of transgender opera singers. Trained as a mezzo-soprano, he risked his singing career when he transitioned several years ago and began taking testosterone, which lowers and alters the voice — a voice he had spent years fine-tuning for opera, where success is measured in the subtlest of gradations.

“A couple of my singer friends were sort of like, you’re ruining your career, you’re ruining your life, the voice is everything,” he recalled recently. “And I thought, it’s not. I would rather enjoy my life, and pursue singing if it happens. I didn’t know if I’d be able to.”