This paper describes a technique of multimodal, multichannel control of electronic musical devices using two control methodologies, the Electromyogram (EMG) and relative position sensing. Requirements for the application of multimodal interaction theory in the musical domain are discussed. We introduce the concept of bidirectional complementarity to characterize the relationship between the component sensing technologies. Each control can be used independently, but together they are mutually complementary. This reveals a fundamental difference from orthogonal systems. The creation of a concert piece based on this system is given as example.