PURPOSE: To synthesize diverse timbre and high-pitch formant sound by multiplying a formant sound pitch by the period waveform of independent desired timbre and a necessary window waveform, and further multiplying the result by a necessary damp waveform.

CONSTITUTION: The window waveform (d) of a modulated wave is generated by the modulated wave generating circuit 3 consisting of a phase accumulator 31, applied with formant band width information BW controlled with a period waveform (b) corresponding to formant sound pitch outputted by a pulse generating circuit such as an accumulator 11 applied with the fundamental frequency information Fo on the fundamental pitch of formant sound pitch, and a sine square or its power circuit 32. A multiplier 5 multiplies this waveform (d) by the period waveform (e) corresponding to the desired timbre of a carrier generating circuit 2 such as an accumulator 21 controlled with a formant center frequency Ff and a multiplier 6 further multiplies the result with an output waveform (g) from a forcible damp waveform memory 4 to easily synthesize a high-pitch formant sound with diverse timbre that a window does not overlap with even when the period of the waveform (b) is shorter than the waveform (d).