The emergence of prosthetic limbs where solely focused on substituting the missing limb with an artificial one, in order for the handicap people to manage their daily life independently. Past research on prosthetic hands has mainly focused on prosthesis' function and performance. Few proposals focused on the entertainment aspect of prosthetic hands. In this research, we considered the defective part as a potential margin for freely designing our bodies, and coming up with new use cases beyond the original function of the limb. Thus, we are not aiming to create anthropomorphic designs or functions of the limbs. By fusing the prosthetic hands and musical instruments, we propose a new prosthetic hand called "MusiArm" that extends the body part's function to become an instrument. MusiArm concept was developed through the dialogue between the handicapped people, engineers and prosthetists using the physical characteristics of the handicapped people as a "new value" that only the handicapped person can possess. We asked handicapped people who cannot play musical instruments, as well as people who do not usually play instruments, to use prototypes we made. As a result of the usability tests, using MusiArm, we made a part of the body function as a musical instrument, drawing out the unique expression methods of individuals, and enjoying the performance and clarify the possibility of showing interests.