PURPOSE: To add the effect of drill playing technique to an input musical sound waveform by digital signal processing.

CONSTITUTION: After an AM modulation part 401 imposes AM modulation on an input musical sound signal W(INP) with plural LFO signals W(LF1)-W(LF 3) generated by an LFO signal generation part 402, a distortion processing part 404 performs distortion processing and a filtering processing part 405 performs filtering processing. At this time, a frequency response nearby the resonance of the filtering processing part 405 varies with variable filter coefficients W(DF1)-W(DF3) generated by a filter coefficient generation part 403 on the basis of the LFO signals. A mixing processing part 406 mixes output signals W(F10)-W(F30) of the filtering processing part 405 to generate output signals W(LOT) and W(ROT) to which the effect of the drill playing technique is added.