We present a novel user interface device based around ferromagnetic sensing. The physical form of the interface can easily be reconfigured by simply adding and removing a variety of ferromagnetic objects to the device’s sensing surface. This allows the user to change the physical form of the interface resulting in a variety of different interaction modes. When used in a musical context, the performer can leverage the physical reconfiguration of the device to affect the method of playing and ultimately the sound produced. We describe the implementation of the sensing system, along with a range of mapping techniques used to transform the sensor data into musical output, including both the direct synthesis of sound and also the generation of MIDI data for use with Ableton Live. We conclude with a discussion of future directions for the device.