In teaching situations, teachers constantly have to make spontaneous and more or less planned choices based on input from pupils, adapted to the specific school setting and within society's social and cultural norms. Two phenomena underpinning such a view on teacher practices are teacher agency and teacher improvisation. The focus of this article is to explore and discuss the relationship between these two phenomena and, more specifically, the role of teacher agency in teachers' capacity to improvise professionally in the classroom. The empirical background for this article is a qualitative study where we have observed and interviewed professional teachers and student teachers within the field of music in a Norwegian culture school and secondary school. The perspective of experience plays a central role in the study and gives us the opportunity to discuss what implications this research could have for teacher education.