Vivian Perlis, a musicologist who founded Yale University’s Oral History of American Music, an invaluable archive of audio and video interviews that she directed for more than 40 years, died on July 4 at her home in Weston, Conn. She was 91.

Her family announced the death.

The oral history project includes some 3,000 recordings of interviews with composers and other major musical figures, from Aaron Copland to Elliott Carter, from Duke Ellington to John Adams. The eminent musicologist H. Wiley Hitchcock described it as an “incomparable resource.”

Ms. Perlis came to run the project accidentally, after taking a job as a research librarian at the Yale School of Music in 1967. She had become involved there with the library’s extensive Charles Ives collection, and one day she made a visit to New York City to pick up some additional materials donated by Julian Myrick, who had been a partner with Ives in an insurance business.

Thinking that he might have some recollections to share, Ms. Perlis brought along a portable tape recorder. She was fascinated by the stories that Mr. Myrick, an elderly, hard-of-hearing former Southerner, told about the iconoclastic, curmudgeonly Ives.