As a player inputs a performance of a music piece by playing a musical instrument or singing a song, an add-on apparatus automatically starts an add-on progression such as an accompaniment to the music piece, a score and word display of the music piece and a picture display for the music piece. The apparatus stores a plurality of accompaniment or score-and-word or picture data files each corresponding to each of a plurality of music pieces. The apparatus recognizes the music piece under the performance inputted by the player, selects the accompaniment or score-and-word or picture date file which corresponds to the recognized music piece, and causes the accompaniment progression or score-and-word display or picture display to start automatically and run along with the progression of the music piece automatically.