PURPOSE: To obtain a consistent tone quality change by storing and setting waveform information subjected to filtering varied according to strong touch and weak touch to a key and weighting these waveform information and synthesizing them thereafter.

CONSTITUTION: Waveform information obtained by subjecting waveform information to filtering varied according to at least strong touch and weak touch to a key 1 are stored and set in a storage means 11. These waveform information are read out and are weighted by key touch information based on individual touch curves respectively and are synthesized by a synthesizer 5 to obtain one musical sound waveform signal. Thus, the musical sound whose hue is changed in accordance with the change of touch to the key can be produced, and the consistent tone quality change unified for the change of key touch is obtained.