A display device displays a musical score image where musical notes indicative of individual tones or sounds constituting a music piece are arranged on a time axis and pitch axis. Pitch information indicative of one or more pitches is acquired in response to an operation on a keyboard, and a note matching any one of the one or more pitches indicated by the acquired pitch information is identified from among the notes included in the musical score image. When any note has been identified as matching any one of the one or more pitches indicated by the acquired pitch information, a display style of the matching note is changed. Only when no note has been identified as matching any one of the one or more pitches indicated by the acquired pitch information, a display mode of a portion of the musical score image other than the notes is changed.