The Sonik Spring is a portable and wireless digital instrument, created for real-time synthesis and control of sound. It brings together different types of sensory input, linking gestural motion and kinesthetic feedback to the production of sound. The interface consists of a 15-inch spring with unique flexibility, which allows multiple degrees of variation in its shape and length. The design of the instrument is described and its features discussed. Three performance modes are detailed highlighting the instrument’s expressive potential and wide range of functionality.