To realize an effect capable of always obtaining an output signal of a natural auditory.

A doubling effector is provided with a voice signal generating part 40 and generates a voice signal by performing pitch conversion processing to an input signal by a pitch conversion part 47, and outputs a mixture of the voice signal and the input signal. In this case, a scale note presumption part 43 presumes a scale note corresponding to the input signal, and when the presumption is completed, the pitch conversion part 47 generates the voice signal by performing pitch conversion so as to bring the pitch of the input signal close to the pitch of the presumed scale note. Further, it is recommended to generate the voice signal only when the scale note presumption part 43 could presume the scale note.