Poststructuralist and socialconstructionist research has focused interactions between individuals, and accordingly objectified materiality. As a contrast, with posthumanist theory materiality can be understood as an actor, which we find interesting to explore further. In music teaching music instruments have a central function, and the activities in the classroom can be said to revolve around a material node, constituted by the instruments. Music teaching is also an arena for identity formation through the variety of identity opportunities that popular culture brings into the classroom. From a posthumanist point of view, identities are in becoming through the combinations of agency of musical instruments and human actors. The aim of this paper is to study the becoming of identities and subject positions in a framework where music instruments are understood as actors in music activities. More specific, this is studied 1) by making intra-actions between instruments and students visible, and 2) by analysing identities offered by the music instruments. Based on some examples from our previous projects, focusing interaction in the classroom, a re-analysis will be made with respect to agency of materiality in ensemble situations. Thus, our ambition is also to explore a new entry to music education research where music instruments take a more central position in our understanding of classroom intra-actions. What happens, for example, in the intersection between specific instruments and gender? How do instruments and students become related dependent on the student’s skills on the instrument in question? What subject positions are possible in an ensemble, depending on which instrument the student is intra-acting with? What happens if a student’s identity does not match an instrument’s identity offer? Such issues appear to be important in order to fully understand parameters that are active in different situations in music education.Within this perspective, different ways of handling the subject have evolved which we find both interesting and important to further explore. The aim of the study is to analyze and problematize posthumanist subjects in pedagogical research. Thus, the ambition is to clarify subject formations and specify subjects that appear, which in turn contributes to visualizing different subject forms. Methodological tools from posthumanist theory are used to find different Entrances in the research Rhizome. The findings are presented as specific Entrances in the Rhizome. The Entrances show different subject formations, where subjects with similarities to poststructuralist perspectives, subjects in a critical framework, as well as more radical posthumanist subjects emerge. Finally, the subject variation that has appeared is further discussed and problematized.