We propose a method that uses music jamming as a tool for the design of musical instruments. Both designers and musicians collaborate in the music making process for the subsequent development of individual "music performer's profiles" which account for four dimensions: (i) movements and embodiment, (ii) musical preferences, (iii) difficulties, and (iv) capabilities. These profiles converge into proposed prototypes that transform into final designs after experts and performers' examination and feedback. We ground this method in the context of physically disabled musicians, and we show that the method provides a decolonial view to disability, as its purpose moves from the classical view of technology as an aid for allowing disabled communities to access well-established instruments, towards a new paradigm where technologies are used for the augmentation of expressive capabilities, the strengthening of social engagement, and the empowerment of music makers.