The only thing (if anything) distinguishing one “Turandot” revival from the following year’s is the singers. So while I kept my eyes open this week during “Norma,” “Hoffmann” and “Flute,” I tried extra hard to focus solely on what the Met has been demanding of me in subway posters all over the city: Hear the voice.

The results were impressive; the company seems to be taking to heart its own marketing copy. This was proved above all by the opening-night “Norma,” whose urgency emerged far more from the exciting singing than the dimly lit production. (The voice must be heard, and nothing must be seen?)

Sondra Radvanovsky returned to the title role, which she played here four years ago; her pungent, chicory-flecked voice was more settled now, less blazing and more calmly confident. And while she is still not a detailed actress — Norma’s final act of self-sacrifice seemed just as unmotivated as the last time she did it — the vocal fireworks and sudden high, soft notes came across less as showy effects this time around.

As for her co-stars, there’s always something affecting in Joseph Calleja’s plangent, slightly nasal tenor, always a sense of tears being held back. Joyce DiDonato may push sharp and grow edgy as her voice gets to its highest reaches, but lower down the sound is cashmere.