Over Watch is an audio/visual performance for two musicians, involving the production of narrative visuals on-the-fly. Presented in a theatrical context, with the musicians playing beneath a large projection screen, the piece references early silent movies, specifically the expressionist films of the 1920s. However, rather than responding to the formal and narrative content of the images onscreen, the musicians in Over Watch have a direct impact upon the content and structure of the movie. The improvised musical score, translated into MIDI and audio data is used to provide camera, lighting and animation cues for a 3D engine, allowing the musicians to effectively direct a Computer Graphic film in real-time.