Packet stream is generated by combining a plurality of packets corresponding to style-of-rendition identification information which are selected from among a number of packets usable for producing waveforms corresponding to various styles of rendition. Then, a waveform having characteristics of the style of rendition indicated by the style-of-rendition identification information is produced on the basis of the generated packet stream. The packet stream includes a plurality of packets and time information of the individual packets and controls the pitch, amplitude and shape of the waveform to be produced. By thus combining packets corresponding to the style-of-rendition identification information and producing a waveform on the basis of the packet stream, there can be provided a waveform corresponding to a desired style of rendition in a simplified manner with great facility.