This paper is devoted to the understudied issue of formation of the semi-documentary genre of radio film. This is the first part of the study, which focuses on the genesis and development of this genre in Russian radio broadcasting in 1920-1940. The objectives of this work are to identify the genre characteristics of radio film, define its place in the genre structure of radio journalism and trace the evolution of the genre throughout the stated period. Special attention in the paper is given to the way radio film was affected by technological change (in particular, new methods of sound recording) and also by the practices of dramatic theatre and cinema. Methodologically, the paper is based on historical and comparative analysis and archive materials. The need for this study is accounted for by the fact that the topic is understudied and by the authors' intention to clarify the terminological confusion that exists among theorists and practitioners regarding this genre. The paper analyzes the programs of the 1920s-1930s on Moscow and Leningrad radio. The study showed that radio film emerged in the formative years of radio broadcasting. The first experiments in this genre were in fact radio plays. The next development stage consisted in an opportunity to record sound on a film. The "Radiofilm" factory produced programs using this technology, the programs being referred to as "sounding chronicles". The genre eventually took shape in the post-war years, when the technological basis of broadcasting drastically changed and most radio programs were recorded on a tape with subsequent editing. An intrinsic quality of radio film is the presence, or rather dominance, of documentary sound records forming a single storyline. Phonodocuments are, on the one hand, the major structural element of radio film; on the other, they are the main expressive means used in this genre.
