The display design for the musical walking stick, as shown.
FIG. 1 is a top perspective view of a front elevation, illustrating the design of my musical walking stick. The left side view and the right side view mirror FIG. 1; and,
FIG. 2 is a bottom perspective of a back elevation thereof.
The broken line showing of a music button in FIG. 2 is for illustrative purposes only and forms no part of the claimed design.