A CPU detects an operation state on a fingerboard at a prescribed period, stores the detected operation state in a memory every time an operation state is detected, detects whether or not any of a plurality of extended strings has been struck, determines a pitch of a note to be played based on the operation state stored in the memory in response to a string being struck, and controls a note to be played in a sound source based on the detected operation state and the operation state stored in the memory every time the operation state is detected after a command to play a note of a determined pitch is issued to the sound source.