Sound subseries primarily relates to the music synthesizer, but does contain some materials on "hi fi," sound on film, and the phonetic typewriter. The first three folders were bound together: Origin of Stereographic Sound; Origin of High Fidelity; and Synthesis of Music. These folders contain research articles and, in some cases, an additional handwritten note. There are several recordings of the music synthesizer between 1952 and 1961. There are four phonographic records and five sound tape reels. The sound tape reels have an accompanying handwritten explanation written by Belar in 1995 at the request of his daughter. There are letters from Belar he wrote to M.W. Scheldorf in response to an inquiry about sounds of music. In 1955 RCA released a four phonographic record box set with a booklet titled; "The Sounds and Music of the RCA Electronic Music Synthesizer." It features narration about the characteristics of musical sounds and musical excerpts demonstrating the synthesizer. Additionally, there is a 16mm film which contains a test method for audio sound on film. There is a videocassette (VHS) copy of the film in the collection. Finally, there is a script for practicing the phonetic typewriter.