What does it mean for an instrumentalist to learn? What is learned, and how? In answering these and other questions, this work intertwines the phenomenological dimension of performance experience with scientific and didactic perspectives. It thus weaves together the core tenets of 'being in music' within the instrumentalist's perception, the technical-musical competencies of the accordionist in dialogue with their instrument, and the functionality of the related learning processes from a scientific viewpoint. The resulting guidelines are translated into methodological frameworks focused on the on the practice-led research process and subsequently articulated into reasoned instructional pathways for initial training. Concurrently, it outlines the characteristics of repertoires, learning contexts and the roles of teacher and student within the framework of enactive pedagogy. Combining operational rigor with an openness toward research, this book is addressed to those interested in general instrumental methodology, and specifically to students of accordion pedagogy, teachers and concert artists interested in metacognitive processes and the development of musicians' expertise.