Soundtracks and music are key elements of narrative and emotional expression in anime, which is a prominently popular animation genre. Nevertheless, the music used in the early decades of Japanese animation production does not have the same sonority and functionality that the music of contemporary anime. Thus, in this paper we analyze the music of the early years of Japanese animation, from the 30s to the 50s, focusing on its different functions, characteristics forms and techniques, the most representative composers, and the most remarkable animations works relative to their characteristic musical aspects. We will show how, in general, these soundtracks were highly influenced by the musical pieces of western animation that arrived in Japan during the period studied. [ABSTRACT FROM AUTHOR]