This paper presents WAS-X (Waseda Anthropomorphic Saxophonist robot X), a saxophonist robot designed following an “Instrument-centered” approach. WAS-X can play on a regular alto saxophone two octaves of music with a direct MIDI input control, but it is much smaller and simpler to control than its WAS predecessors and can be used in the future for more complex interaction studies. In developing this robot, we used a Design Thinking method with the goal of solving the “wicked problem” of finding a balanced solution between performance quality and dynamic movement freedom for interaction purposes. From a Design Thinking perspective, we replaced “User-centered design” with an innovative “Instrument-centered design” and explored different development alternatives, ultimately focusing on the human holding posture of the saxophone by observing saxophonists and following how beginners learn to play the saxophone.