n research (2010-2012) conducted by the research group Lifelong Learning in Music into instrumental lessons for elderly learners, a ‘Community of Practice’ (CoP; Wenger & Lave) was set up in which instrumental music teachers exchanged expertise and reflected together on their actions in lessons with elderly pupils. Meetings of the CoP centred on the exchange and development of knowledge. In 2012-2013 a follow-up study was conducted which looked into the transfer and development of knowledge within this CoP. Central in this follow-up study were the questions: “What learning takes place in the CoP?” and “Can collaborative learning contribute to the professional development of teachers?”