Transitions towards sustainable societies increasingly require multi-perspective and transdisciplinary approaches not only theoretically but also at the practical and policy levels. This theory-oriented chapter explores the potential of transdisciplinary professional repositioning through the case of a language-aware choir that aims to respond to the real-life needs of its adult immigrant participants by merging learning Finnish as a second language into a choir practice. By interrogating the idea of artistic autonomy as a principle that has in effect prevented music professionals from identifying meaningful opportunities for new practices, the chapter lays the ground for conceptualizing language-aware choir practice as an invitational practice and an emerging double-focus activity system. The chapter argues for a transdisciplinary transition from the stable and narrow understanding of professional expertise in music education towards accepting the potential of music education to play a central role in transdisciplinary approaches in seeking ways out of unsustainability. The theoretical argument is supported by data from two language-aware choirs that illustrate how the constantly co-developed transdisciplinary fusion of two activity systems, namely choir and second-language class, can strengthen choir participants’ active being-in-society and expand music educators’ professional horizons beyond the established unidisciplinary boundaries.