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.