Music piece sequence data are composed of a plurality of event data which include performance event data and user event data designed for linking a voice to progression of a music piece. A plurality of voice data files are stored in a memory separately from the music piece sequence data. In music piece reproduction, the individual event data of the music piece sequence data are sequentially read out, and a tone signal is generated in response to each readout of the performance event data. In the meantime, a voice reproduction instruction is output in response to each readout of the user event data. In accordance with the voice reproduction instruction, a voice data file is selected from among the voice data files stored in the memory, and a voice signal is generated on the basis of each read-out voice data.