Letters, mostly manuscript, and copies of letters in letterpress copybooks. Outgoing correspondence, kept in letterpress copybooks, include letters to family, friends, and musical colleagues. Incoming correspondence includes letters from famous composers and musicians. Correspondence to and from others includes letters to and from friends and colleagues C.B. Cady and Otto Floersheim, with whom Gleason worked closely, as well as letters to Gleason’s father-in-law J.A. Kennicott.