This paper reviews and extends questions of the scope of an interactive musical instrument and mapping strategies for expressive performance. We apply notions of embodiment and affordance to characterize gestural instruments. We note that the democratization of sensor technology in consumer devices has extended the cultural contexts for interaction. We revisit questions of mapping drawing upon the theory of affordances to consider mapping and instrument together. This is applied to recent work by the , , author and his collaborators in the development of instruments based on mobile devices designed for specific performance situations.