Informal learning has become a prominent theme in music education literature in recent times. Many writers have called for a new emphasis on informal knowledge and pedagogy as the way forward for music education. The position taken in this paper is that a central issue for music education is the accommodation of a tension between types of knowledge and the ways of knowing strongly associated with popular and classical of music--socially acquired informal knowledge and socially developed but formally acquired disciplinary knowledge. Approaches to curriculum conception and realisation observed in a recent series of case studies in New Zealand secondary schools suggest that a key factor in student engagement is the degree to which teachers can create links between informal and formal knowledge so that students' understanding and conceptual abilities can be extended across these knowledge boundaries. The teaching approaches of two recent graduates in rock music are discussed to support the social realist argument that a "progressive" approach to curriculum involves creating links between informal and formal knowledge rather than replacing one with the other or dissolving the boundaries between them. Through seeing the two types of knowledge as necessarily interconnected within educational contexts, the epistemic integrity of classroom music is maintained. In this way students are able to recognise themselves and their aspirations while also recognising the potential and power of the foundational knowledge of the discipline.