Abstract: The differentiation data of a basic waveform is read out from a differentiated value waveform memory at a clock timing corresponding to a musical scale of an operated play key, and it is multiplied by an envelope value of a musical sound waveform to form a musical sound waveform differentiation value. In parallel therewith, the differentiation data is accumulated at the clock timing to form a compensative value. The compensative value is added with the musical sound waveform differentiation value at the point of time at which the envelope value is changed to cancel a DC component which would otherwise develop in a produced musical sound waveform. The musical sound waveform differentiation values thus compensated are accumulated, and are subjected to digital-to-analog conversion, so that the musical sound waveform free from the DC component is produced.