In an electronic keyboard instrument (1) being an example of a musical performance apparatus having a musical operation unit, a unique musical performance apparatus is formed by an outer face of its exterior (2), and part or a whole of the outer face of the exterior (2) is formed as a temperature sensitive discolorable layer, for example, as shown by the hatched outer faces of upper side panels (22), lower side panels (23), and a back panel (25), so that at least part of the exterior (2) changes in color according to a change in environmental temperature or a temperature change caused by radiant heat by illumination of lights (34). In order to forcibly discolor the temperature sensitive discolorable layer of the exterior (2), it is preferable that heaters or Peltier modules are incorporated in the exterior (2) and electricity is supplied thereto for enabling heating, or heating and cooling.