An electronic musical instrument comprises an automatic rhythm performance device, an automatic bass chord performance device and an automatic arpeggio performance device. Each device has its own start-stop control circuit and a control in/out terminal. When a device is start-stop controlled, a control signal appears at the control in/out terminal, whereas if a control signal is externally applied to the control in/out terminal, the device is start-stop controlled. The control in/out terminals of the respective devices are connected together by a common line so that a start-stop of one device causes the start-stop of other devices.