After the marriage ended, Ms. Ridley established herself underground. She became affiliated with the Metropolitan Transportation Authority’s Music Under New York, a program under which selected musicians perform in the transit system. She appeared twice a week at a designated spot. She said that no money was ever stolen from her and she was never assaulted.

And she developed her act, learning to work an audience that wasn’t inclined to stand still. She figures that thousands of commuters over the years have sung duets with her.

Ms. Ridley relishes these connections: “We’re face to face,” she said, describing the appeal of busking.

Subway singer going up