This paper proposes an interface based on melodic input, encouraging a user to sing in order to interact with a device. We describe the early stages of designing and prototyping a sound-reactive shower, which is controlled by a user singing to control the flow of water. We then discuss the implications of this design with regards to energy and resource efficiency, as well as being a form of provocation and experimental interface design. Interaction design has an important role to play in facilitating sustainable behaviour in the household. We propose that sonic interfaces such as this can contribute to this area of work, and that an interface based on melodic input can be used to seamlessly activate and deactivate a system while using hands and vision to accomplish other actions and reducing energy consumption. In this paper, the prototype is described, evaluated and results are discussed. Finally, directions for future work and extensions of this system are proposed.