Increases in the cultural and ethnic diversity of many societies since the mid-twentieth century and the reality of the multicultural classrooms within which school teachers work today have led many educators to believe there is a need for students to develop greater intercultural understanding (Draisey-Collishaw, 2004; Hayden & Thompson, 1998). Many music education policies and curricula have changed to incorporate a broader view of what types of music should be studied in schools (Volk, 2004). One approach to developing more culturally responsive and diverse programs for music learning and teaching has been to introduce into schools a range of musics and ensembles, such as Indonesian gamelan. Gamelan are traditional instrumental ensembles from Indonesia and Malaysia consisting largely of bronze or iron metallophones, gongs of various shapes and sizes, and drums. This thesis explores the attitudes, beliefs, approaches and experiences of teachers in the context of teaching and learning Indonesian gamelan in schools in Australia and New Zealand. Gamelan in schools in Australia and New Zealand exist in a range of contexts. Some form the basis of vibrant and innovative educational programs with wide-reaching effects. Others, after an initial period of activity, spend years in school storerooms and are rarely, if ever, used again. Considering the rarity and cost of a set of these instruments, and their significant potential for teaching intercultural understanding in addition to a wide range of musical skills, why are some of these gamelan so underused? What factors affect the vitality and sustainability of school-based gamelan programs? This project examines teachers’ perspectives on school-based gamelan programs and, in particular, investigates the myriad influences on the sustainability and vitality of such programs. Data collection involved semi-structured interviews with teachers and representatives of school management in 23 schools in Australia and New Zealand with gamelan programs. I modified the Music Vitality and Endangerment Framework (Grant, 2014, p. 111) for use as an instrument to initiate discussion with interviewees about their specific programs and contexts, explore and describe these school-based gamelan programs and compare programs across schools. The Introduction (Chapter 1) to this thesis presents the context and rationale for my research, the research question and aims. Chapters 2 and 3 comprise a review of relevant scholarly literature, publications and curriculum documents relating to cultural diversity in music education and literature concerning teaching and learning gamelan. Chapter 4 details the study’s methodology and theoretical and conceptual frameworks, as well as the research design, data collection and analysis methods. Chapter 5 presents the findings from the data analysis. Chapters 6 and 7 describe and examine the stages involved in my development of a theoretical framework for gauging the vitality and sustainability of culturally diverse music (CDM) programs in schools. Chapter 8 concludes the thesis, discusses the research outcomes and provides recommendations for action and future research. This study aims to shed light on a little-explored aspect of CDM education in Australia and New Zealand and to contribute to scholarly understanding of the role that CDM programs can and do play in school-based education in Western countries. The insights gained from this research project may help educators, school management, policymakers and community stakeholders better support the vitality and sustainability of gamelan and other CDM programs in schools, and thus help students reap the many potential benefits of these programs.