In the pitch-dark auditorium of Rome’s Teatro Costanzi, a high-pitched lament floated from the top galleries. Dozens of flashlights snapped on, their beams crisscrossing crazily, seeking the source of the sound.

The shafts of light homed in on a spectral figure — a slim, dark-haired woman dressed in white, moving at a funereal pace and plaintively singing. In the audience, 130-odd children, ages 8 to 10, let loose squeals, some gasps, and one “it’s not real.” Several called out “Emma, Emma.”

The children had just been told that the Costanzi, the capital’s opera house, had a resident phantom. No, not that one. This was said to be the spirit of Emma Carelli, an Italian soprano who managed the theater a century ago, and loved it so much that she was loath to leave it, even in death.

“The theater is a place where strange things happen, where what is impossible becomes possible,” Francesco Giambrone, the Costanzi’s general manager, told the children Saturday afternoon when they arrived to participate in a get-to-know-the-theater-sleepover.