Implementation of F0 transformation for statistical singing voice conversion based on direct waveform modification

This paper presents a technique for transforming F₀ in a framework of statistical singing voice conversion with direct waveform modification based on spectrum differential (DIFFSVC). The DIFFSVC method converts voice timbre of singing voices of a source singer into that of a target singer without using vocoder-based waveform generation. Although this method achieves high sound quality of the converted singing voices, its use is limited to only intra-gender conversion without the need of F₀ transformation. To make it possible to also use the DIFFSVC method for cross-gender conversion, we propose a method to transform F₀ of an input singing voice for the DIFFSVC. The proposed method is also based on direct waveform modification using overlap-add process and filtering process. Results of subjective evaluations demonstrate that the proposed DIFFSVC method with F₀ transformation significantly improves sound quality of the converted singing voices while preserving the conversion accuracy of singer identity in the cross-gender conversion compared to the conventional SVC with vocoder.