Controlling Interactive Music (CIM) is an interactive music system for human-computer duets. Designed as a creativity support system it explores the metaphor of human-machine symbiosis, where the phenomeno- logical experience of interacting with CIM has both a degree of instrumentality and a sense of partner- ship. Building on Pachet's (2006) notion of reflexiv- ity, Young's (2009) explorations of conversational in- teraction protocols, and Whalley's (2012) experiments in networked human-computer music interaction, as well as our own previous work in interactive music systems (Gifford & Brown 2011), CIM applies an ac- tivity/relationality/prominence based model of musical duet interaction. Evaluation of the system from both audience and performer perspectives yielded consen- sus views that interacting with CIM evokes a sense of agency, stimulates creativity, and is engaging.