The object of the invention is to switch between plural sets of waveform data at desired timing while preventing noise. In response to an instruction for switching from a currently reproduced set of waveform data to another set of waveform data, either a switching position in the other set of waveform data or a switching in the currently reproduced set of waveform data is set as end timing for ending the reproduction of the currently reproduced set, with reference to switching position information of the two sets. If the switching position in the currently reproduced set is present within a 50 msec time range before a switching position in the other set that is present immediately after the switching instruction, the switching position in the currently reproduced set is set as the ending; if not, the switching position in the other set is set as the end timing.