This paper describes the concept, design, realization and evaluation of a radically augmented musical instrument named the Overtone Violin. The rationale behind the development of the instrument is to preserve the expressive elements of the expert violinist, while incorporating the added benefits of gestural controllers via embedded sensors. There have been many examples of idiosyncratic alternate controllers in electronic music, as well as quite a few hybrid controllers that typically use sensors to capture the motions of playing a traditional instrument. However the Overtone Violin crosses these boundaries by retaining the original violin techniques and sounds as well as extending/enhancing the instrument with new methods of expression that are not inherent to the conventional technique.