In a music system, an input unit is manipulated for inputting a signal representative of a performance operation amount rendered by a performer, and an output unit is provided for outputting a music sound in response to the signal fed from the input unit. The input unit has a grip part that is grasped by the performer and shaped to receive a dynamic pressure caused from grasping by the performer for inputting the performance operation amount. A conversion part is provided in the input unit for converting the dynamic pressure applied by the performer into a force acting in a specified direction. A detection part is positioned to align a sensitivity thereof with the specified direction for sensing the force generated by the conversion part and outputting the signal indicative of the performance operation amount in response to the sensed force.