Fortunately, the science fascinated her. She knew how to sing, but she had never understood how she sang, the precise mechanics of breath, mouth and vocal folds. That might have been the end of it, as she was soon hired by the Light Opera of Manhattan as a mezzo soprano. But even as she pursued a performing career, Lader could not let go of vocal therapy. Knowing that she was a singer, she said that Mount Sinai Hospital, where she had completed an externship, began to refer injured singers to her, trusting her with their rehabilitation. A few years later, she rented the Union Square studio and relinquished performance. She has been booked solid ever since.

Much of her work still deals with rehabilitation. She helps singers dealing with polyps, nodules, hemorrhages, cysts, acid reflux, vocal fold swelling. (She showed me a terrifying slide show depicting these various ailments and disorders.)

LuPone first met with Lader in the mid-’90s, after a vocal cord operation.

“I couldn’t talk, I had nothing,” LuPone said. Lader began with Lupone’s speaking voice, then rehabbed her singing voice. “She saved my career,” LuPone said. “She gave me a technique to allow me to continue to sing with the strength and the clarity that I’ve had ever since.”

Billy Porter contacted Lader in the early 2000s, having lost his voice to acid reflux. Porter’s voice had always had a gospel sound, a rock sound, which was atypical of Broadway performers back then. During their sessions, Lader never tried to change that. “She was one of the first teachers that I met who was not about squashing that,” Porter said.

The other side of her practice involves healthy singers who are new to a role, who are struggling in a role, or who want to expand and improve their voices. Often performers come to her in a kind of existential panic, because they no longer understand how they do what they do. She encourages singers to relax and to open their whole throats, which isn’t always comfortable.