This book traces the research on the design, implementation and outcomes of a professional development program for in-service primary and secondary school teachers aimed at enhancing their understanding of living music traditions in Singapore and how these could be taught in the 21st century music classroom. It proposes a professional development framework comprising the areas of Pedagogy, Practice and Perspective to guide professional development design. The book also aims to promote further discussions on adult learning and teaching about teaching, especially with regard to developing self-efficacy to handle different music traditions in a 21st century, multi-ethnic society like Singapore.