An electronic musical instrument is composed of a main body portion and parts such as an upper keyboard, a lower keyboard, and so on that are selected from among parts of a high-grade and low-grade in accordance with the model thereof and placed in the main body portion, in which a ROM stores control programs necessary for control of the electronic musical instrument of the high-grade model and low-grade model so that a CPU selects any of these and executes it. The selection is performed in accordance with an ON/OFF state of a limit switch provided to correspond to one of the parts. A portion of the part is made to have a different shape depending on the grade, so that when the part is placed in the main body portion, the limit switch comes into an ON/OFF state in accordance with the grade of the part.