A CPU 21 sequentially changes over plural music pieces and reproduces the same by a program processing. Upon the changeover of the music piece, the volume of the tone signal that is being generated at each tone generating channel in a tone generating circuit 14 is gradually decreased, whereby the tone signal is finally faded out. The volume decreasing speed in this case is such that the higher the priority order of the performance data is, the slower the speed is. The generation of a tone signal based upon performance data of next music piece data is assigned one after another from a tone generating channel wherein a fade-out has been completed. The volume of the assigned tone signal is controlled so as to gradually increased, whereby the tone signal is faded in. In this case, the assignment of the generation of the tone signal based upon the performance data of the next music piece is made earlier, as the order of priority of the performance data is higher. A first music piece and second music piece can be naturally changed over and reproduced as cross-faded without preparing plural tone generating circuit systems.