Two related versions of an unstable live algorithm for the Disklavier player piano are presented. The underlying generative feedback system consists of four virtual musicians, listening to each other in a circular configuration. There is no temporal form, and all parameters of the system are controlled by the performer through an intricate but direct mapping, in an attempt to combine the experienced musician’s physical control of gesture and phrasing, with the structural complexities and richness of generative music. In the first version, Circle Squared, the interface is an array of pressure sensors, and the performer performs on the system without participating directly, like a puppet master. In the second version, control parameters are derived directly from playing on the same piano that performs the output of the system. Here, the performer both plays with and on the system in an intricate dance with the unpredictable output of the unstable virtual ensemble. The underlying mapping strategies are presented, together with the structure of the generative system. Experiences from a series of performances are discussed, primarily from the perspective of the improvising musician.