I would like to begin by examining the title, since this will clarify the theoretical framework within which this paper will develop. Chambers Dictionary (1988) defines dynamic as relating to force; activity or things in motion; forms or patterns of growth or change; any driving force instrumental in growth or change. The word interplay refers to the reciprocal, mutual musical interaction between therapist and patient. Both players' contributions help to clarify the quality of the emotional interaction in the musical relationship. The concept of clinical improvisation in music therapy is best illustrated by a detour via the literature of mother-infant interaction.