This paper describes the concept, design, and realization of two iterations of a new controller called the XT Synth. The development of the instrument came from the desire to maintain the expressivity and familiarity of string instruments, while adding the flexibility and power usually found in keyboard controllers. There are different examples of instruments that bring the physicality and expressiveness of acoustic instruments into electronic music, from "Do it yourself" (DIY) products to commercially available ones. This paper discusses the process and the challenges faced when creating a DIY musical instrument and then subsequently transforming the instrument into a product suitable for commercialization.