This paper presents the soma design process of creating Body Electric: A novel interface for the capture and use of biofeedback signals and physiological changes generated in the body by breathing, during singing. This NIME design is grounded in the performer's experience of, and relationship to, their body and their voice. We show that NIME design using principles from soma design can offer creative opportunities in developing novel sensing mechanisms, which can in turn inform composition and further elicit curious engagements between performer and artefact, disrupting notions of performer-led control. As contributions, this work 1) offers an example of NIME design for situated living, feeling, performing bodies, and 2) presents the rich potential of soma design as a path for designing in this context.