The CV Drum Tracker is a cybernetic extension of the drumset that aims to reshape the performer's interaction and musical relationship with the acoustic instrument. It prompts users to embrace a systems-oriented, iterative method of design and performance, to explore the gestural and musical potentialities in a space where they serve as mediators between the physical instrument and its virtual components. In digital design, affordances actualized by the end-user correspond to the inherent constraints integrated within the system. The establishment of these constraints transpires through parameter mapping, and the perceptual affordances of a given system manifest as the user scrutinizes and navigates its predetermined boundaries. Each design phase culminating in the current iteration is presented and discussed through an analytical framework centered on constraints and affordances. This framework serves to highlight the dynamic relationship existing between these two crucial components in any interactive digital music software, and the procedural nature by which these design relationships formulate for both the programmer and performer of the system.