Musikdidaktik is a central subject within music teacher training in the Nordic countries. In musikdidaktik acts of teaching (music) and learning (musikdidaktik) constitute possibilities for identity formation. The objective of learning is closely connected to their future profession, in which musical and educational competences are blended, combined and used in different ways. The study presented in this article was based on a phenomenological way of thinking about education as an arena for identity development. Students' identity formation in relation to their education in musikdidaktik was investigated. In an interview study where seven musikdidaktik professors and three groups of music teacher trainees participated, the following questions were asked from a phenomenological perspective: How can education in musikdidaktik function as an arena for identity formation? What constitutes processes of music teacher trainees' identity formation? What connections can be seen between ways of teaching musikdidaktik and identity? What competences (are expected to) develop during the processes and how are they connected to employability? The results show that trainee identity formation processes can be communicated. It became evident that awareness of and reflections upon one's own experiences, learning, goals and identity development are important issues in the trainees' identity formation processes. That the trainees had the possibilities to try to act as music teachers proved to be important. When it comes to the challenges for the professor, they are primarily concerned with handling situations in a way that encourages the growth of the trainees, but also challenges them to reflect; and to be a role model, but also to offer them meetings with different role models. The competences that the trainees develop are combined in different ways within the trainees' identity formation. Musikdidaktik constitutes an arena where the students should have the opportunity to be in the world as music teachers through playing to teach music.