In this paper, I explore the question of agency in spontaneous action via a phenomenology of musical improvisation, drawing on fieldwork conducted with large con- temporary improvising ensembles. I argue that musical improvisation is a form of ‘participatory sense-making’ in which musical decisions unfold via a feedback pro- cess with the evolving musical situation itself. I describe how musicians’ technical expertise is developed alongside a responsive expertise, and how these capacities complicate the sense in which habitual action can be viewed (...) as pre-conscious or ‘automatic.’ Nevertheless, I shall argue that the self-awareness required for expert improvisation does not amount to highly reflective deliberation, arguing instead that the practice of musical improvisation involves an exercise of practical rationality, akin to what Aristotle called phronēsis. Musical decisions – as an expressive form of sense-making – are guided by feelings of ‘rightness’ that are experienced directly and intuitively, responding to the norms and reasons that are embedded in the instruments, sounds, and practices of a particular (sub)culture. (shrink)