The Morton Feldman Collection of Audio Recordings contains 52 reel to reel tapes and 35 cassette recordings, including performances of 38 compositions by Morton Feldman. The collection also includes some events, including the conversations between John Cage and Feldman recorded in 1966 as Radio Happenings I and II, the memorial service for Feldman at St. Mark's Church in New York City, a tribute radio program broadcast by WNYC 7 November 1987 in New York City, and an interview of Jan Williams by Sebastian Claren about Feldman. Other composers represented by recordings include Harrison Birtwistle, Pierre Boulez, John Cage, Barbara Monk Feldman, and Bunita Marcus.

The collection of Slee Lecture Recital Recordings contains 94 reel to reel tapes of lectures by the named Slee Visiting Lecturer in the Music Department at the State University of New York at Buffalo.