Music institutions predominantly utilize the one-to-one lesson in developing and supporting music students' learning of skill and knowledge. This article explores the effect that interpersonal interaction plays in shaping pedagogical applications between teacher and student. Observing the learning of improvisation within this individualized social context, dynamic systems theory (DST) is used to explore how learning and development of musical improvisation skills are shaped by interpersonal behaviors and learning relationships. Through the dimensions of teacher "action" and "affiliation", this phenomenological study investigates the interactive behaviors of five expert Australian educator/improvisers and their students. Interpretative phenomenological analysis is utilized to identify modes of behavioral interactions that evolve through dynamic and fluid interplay. Interactive behavior positions and facilitates the delivery of skill, knowledge, teacher attitudes and understandings of the improvisation process. An interpersonal model of behaviors within the instrumental music lesson is posited, and implications for ongoing critical reflection of interpersonal and pedagogical approaches in the one-to-one context are suggested.