The collection contains Rudolf's extensive correspondence with prominent 20th century musical figures, Metropolitan Opera annual files documenting his years with that organization, and a few photographs of Rudolf alone and with others. Rudolf corresponded with many notable figures from all realms of the music world, including Samuel Barber, Rudolf Bing, Luigi Dallapiccola, Norman Dello Joio, David Diamond, Antal Dorati, Glenn Gould, Erich Leinsdorf, Ira Levin, James Levine, Gian Carlo Menotti, Eugene Ormandy, Gunther Schuller, William Schuman, Rudolf Serkin, Isaac Stern, Georg Szell, and Bruno Walter. His tenure at the Curtis Institue of Music and affiliation with the American Symphony Orchestra League are well documented in this collection. The Metropolitan Opera annual files represent the years Rudolf was active with that organization. Each annual file includes operatic programs (often annotated by Rudolf), Metropolitan Opera annual publications, contracts, correspondence, itineraries, travel-related expense bills, articles, clippings, radio broadcast scripts, press releases, rehearsal schedules, broadsides, and other miscellaneous documents.