The aim of this paper is to define the process of iterative interface design as it pertains to musical performance. Embodying this design approach, the Monome OSC/MIDI USB controller represents a minimalist, open-source hardware device. The open-source nature of the device has allowed for a small group of Monome users to modify the hardware, firmware, and software associated with the interface. These user driven modifications have allowed the re-imagining of the interface for new and novel purposes, beyond even that of the device’s original intentions. With development being driven by a community of users, a device can become several related but unique generations of musical controllers, each one focused on a specific set of needs.