An automatic music performing apparatus comprises a performance memory for storing music performance data of a relative time format including an event group including at least note-on events indicating the note generation start, note-off events indicating the end of the note generation, volume events indicating the volumes of the tone, and tone color events indicating the tone color with the respective events arranged in a music proceeding sequence, and an interval of time interposed between respective two events, wherein the apparatus sequentially reads out the stored music performance data, converts it into note data representing the note generation properties of each note, and stores the note data in a conversion data memory, so that automatic music performance is executed by reading out the stored note data and forming tones corresponding to the note generation properties represented by the read note data.