This thesis assesses the ways in which films related to Dada and Surrealism used sound techniques during the 1920s and 1930s. It argues that their audio-visual approaches were distinctive, and related to important concepts and strategies within the movements such as collage, juxtaposition, and the Surrealist âmarvellous.â Historical research is combined with close analysis and theoretical interpretation to examine the early sound film context in detail, while also bringing a new aural perspective to Dada and Surrealist cinema studies. The project addresses an important, yet neglected, part of film sound history, while also pushing art historical interpretation of these works beyond a long-held visual bias. Dada and Surrealist cinema's heyday coincided with the period of transition from silent to sound film, and several filmmakers associated with these movements, including Luis BuÃ±uel and Salvador DalÃ, Jean Cocteau, and Hans Richter, were at the forefront of this change, producing some of the earliest sound films in their countries of work. Audio-visual experimentation flourished during this period, providing opportunities for these and other filmmakers to try a range of provocative, idiosyncratic methods that prioritised irrationality and sensation. Dada and Surrealist practices were inherently heterogeneous, and their soundtrack approaches were too, mixing silent and sound film methods: from using pre-existing gramophone accompaniments to creating composite sound and image collages, from remixing dance music to silencing the leading lady. Informed by the contemporary debates around asynchrony and counterpoint, I investigate these experiments to establish what Dada or Surrealism audio-visuality actually was. This thesis is essentially a historical corrective, which questions assumptions about this film period, and reinterprets how Dada and Surrealist works fit into it. Case studies of works by BuÃ±uel and DalÃ, Cocteau, Richter, Man Ray, Len Lye, and Joseph Cornell illustrate discussions of pre-existing music use, audio collage techniques, and the role of voices. Sound is demonstrated to have been fundamental in creating the irrational, disorientating, or immersive experiences most valued in Dada and Surrealism film.