In this article I examine the role of the instrument in Evan Johnson and Carl Rosman's collaboration on a new work for eighteenth-century basset clarinet, 'indolentiae ars', a medium to be kept (2015). Drawing on material collected over 30 months -including interviews; audio-visual footage; and correspondence containing sketches, fingering charts, and recordings -I consider the latent practices that lie within the instrument, and their role in the creative process. From the aesthetic discourses that pervaded the musicians' discussions, to the transitional and sometimes 'accidental' moments of instrumental interaction during workshops, I trace the micro-processes within the broader creative trajectory, in order to understand how the instrument's historical, social, and ergonomic affordances were enmeshed within the here-and-now of the collaboration. The article illustrates the dynamic character of collaborative work, shaped not solely by the knowledge of individuals, but through a close reciprocity between perception, action, and the discursive and material conditions of their surroundings.