This paper reports findings from an investigation of the implementation of "assessment for learning" in classroom music instruction in Hong Kong primary schools, focusing on the changes in assessment practice and music teachers' classroom instruction. Qualitative methodology was employed to document the cases of three music teachers. It was found that change in assessment practice in classroom music instruction led to a change in curriculum design which enhanced curricular alignment, as well as change in the mode of instruction which facilitated communication and interaction between teachers and students.[Copyright of Teacher Development is the property of Routledge. Full article may be available at the publisher's website: http://dx.doi.org/10.1080/13664530701644599]