Incoming, and occasionally outgoing correspondence with musicians, composers, colleagues, students, and friends. Also included are autographs, picture postcards, postcard caricatures of the subject, and occasionally concert announcements. There is a significant letter exchange between Ganz and his friend, Nolie Goldstein, where he talks to her at length about his performing and conducting the St. Louis Symphony Orchestra. Since Ganz was fluent in German, French, and English, letters are in various languages and are indicated, unless the entirety of the folder is in English. Some correspondence with famous composers and people, such as Ravel, Bartok, and Schweitzer, were removed and are in other repositories, and what remains in the folder is a Photostat copy of the original.

For more autographs of prominent people, see Ganz's Guestbook. Correspondence with family members is in the Family series.