The purpose of this narrative case study was to describe the developing teacher identity of Nicole Downing, a first-year teacher in the US, in her use of both formal and informal learning processes. As music education continues embracing approaches like informal music learning, it should also reflect on the voices of teachers in the field. Data collection included interviews, observations, and participant writings. Findings revealed that Nicole (a) questioned and eventually accepted her music teacher identity, (b) exhibited a dualism between her use of formal and informal music learning processes, and (c) broadened her community's definition of school music. Nicole used the metaphor of a bruise to describe how she believed some in her undergraduate studies would judge her interest in popular music and creative musicianship, but as she became a music teacher she had agency to incorporate the informal learning she valued. Nicole exhibited a duality in her use of formal and informal learning processes, which were not integrated in her teaching. Ultimately, she developed a broadened definition of school music that she believed was beneficial for students but perceived negatively by other music teachers. Music teacher education should support teachers' diverse identities and continue to explore the teaching strategies used in facilitating informal music learning experiences.