An apparatus is constructed for converting an input voice signal into an output voice signal according to a target voice signal. In the apparatus, an input device provides the input voice signal composed of original sinusoidal components and original residual components other than the original sinusoidal components. An extracting device extracts original attribute data from at least the sinusoidal components of the input voice signal. The original attribute data is characteristic of the input voice signal. A synthesizing device synthesizes new attribute data based on both of the original attribute data derived from the input voice signal and target attribute data being characteristic of the target voice signal composed of target sinusoidal components and target residual components other than the sinusoidal components. The target attribute data is derived from at least the target sinusoidal components. An output device operates based on the new attribute data and either of the original residual component and the target residual component for producing the output voice signal.