In this article, based on a longitudinal study that the author conducted in a primary school in Japan, a methodology for assessing the long-term impact of music education is discussed. With the intention of understanding the meaning of primary music education from the perspectives of the learners, retrospective data were collected from former primary school students who became university students. Methodological possibilities are discussed in the light of nine themes, including the use of retrospective data and video recordings, focus group interviews, the involvement of teachers, subjectivity, and the view of narrative understanding. While most impact case studies pay little attention to how student learning actually takes place, the proposed methodology in this article emphasizes the importance of qualitative understanding in the initial stages as well as underscoring learners' retrospective valuations of their own learning experiences.