The collection contains recordings of 93 of the approximately 173 concerts presented at the Evenings for New Music concerts from 1964-1980. Approximately 464 works were recorded as well as some spoken introductions to works by their respective composers. The original recordings were made on reel-to-reel tapes. The contents were transferred to cassettes in the 1980s and then digitally reformatted in 2007 onto CDs (service and in-house masters) and DVDs (preservation masters).

The collection contains 172 original reel to reel tape recordings of 113 recitals containing approximately 613 works. The works range from the Renaissance to music created for the concerts, even improvised at the events. The reels are accompanied by audio cassette recordings created as service copies and a hard drive containing digitally reformatted preservation and access files.