The New York Public Library for the Performing Arts announced an ambitious program in 1970 to preserve evanescent theatrical performances for posterity on film. Betty L. Corwin was described as assisting the man in charge, the chief of research .

But the project, which would become the renowned Theater on Film and Tape Archive, was the charismatic Ms. Corwin’s baby. She proposed it to the library in 1969 and, told that she could pursue it as a volunteer, coaxed it into being through a feat of extraordinary diplomacy, persuading each theatrical union that recordings would neither lead to piracy nor harm the box office.

“That’s the only way that programs get started,” the Pulitzer Prize-winning playwright Paula Vogel, whom Ms. Corwin hired to be her secretary in the early 1980s, said in an interview. “As one-woman shows.”

Ms. Corwin quickly became the archive’s director and relentless fund-raiser, and remained so until she stepped down in 2000 at 80. She was 98 when she died on Sept. 10 at her home in Weston, Conn.