The rehearsal room where I couldn't make a sound

I'm standing on stage, fully lit, and my mouth moves but nothing comes out. No air, no voice, just this suffocating silence. The conductor keeps gesturing, the pianist keeps playing, and I am the only person in the building who can't make a sound. I woke up with that horrible tightness in my throat — but also kind of grateful, because in real life my voice is right here, waiting for me.