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).