This issue of the world of music is devoted to a topic of enduring importance to ethnomusicology: the sustainability of music cultures. It elaborates on findings drawn from a five-year international research project, Sustainable Futures for Music Cultures, coordinated from Australia by the Queensland Conservatorium Research Centre, Griffith University, Australia, and funded by the Australian Research Council and a range of academic and industry partners. The Sustainable Futures project investigated the notion of music sustainability in nine diverse case studies exploring highly diverse music practices worldwide, revealing the complex relationships between music genres, musicians, audiences and the cultural ecosystems that they inhabit and shape. The comparison of these case studies resulted in the elaboration of a discourse of musical "ecosystems."This volume extends the discourse developed through Sustainable Futures to include six further examples of scholarly engagement with musical ecosystems, together with an introduction that frames the ecosystems approach in relation to current trends in ethnomusicology. It encompasses various professional and academic perspectives on this topic, with contributions from individuals who have occupied diverse positions vis-à-vis their fields of enquiry as scholars, performers, promoters, industry leaders, activists, and teachers. The volume is deliberately international in scope, with contributions from authors in China, India, Australia, New Zealand, the USA, and the UK. While thematically aligned, these contributions maintain distinctive voices, reflecting the differing foci and priorities of the authors themselves, who reside both inside and outside academia. Overall, the volume aims to contribute to the development of theoretical discourses in ethnomusicology by provoking dialogue about musical ecosystems, achieved through the presentation of concrete and applied examples.