The article has two theoretical aims. Firstly, it reconstructs the Schutzian theoretical contribution to musical foundation of interaction. A. Schutz articulated a basic conception of interaction as making music together in contrast with Halbwachs’ professional musician’s communication. In this article, his very important motif will be ascertained by two aspects of his early work “The meaning of opera” and Husserlian phenomenological terms. Secondly, it proposes to develop this result up to a more general level of social system theory. Following the social system theoretical distinction of form and medium by F. Heider and N. Luhmann, we are asking how we could grasp music as form. Even if we presuppose not only a notation but also three elements of music of rhythm, melody, and harmony as form, sensory perceptions and bodily movements remain to exist residually, because they are symbiotically mediated through body and language. In other words, body and language, both of which also are mediums, are mediated through another medium of music. Therefore, we intend to conceptualize music as intermediary medium for interaction.