A singing voice edit assistance method, performed by a computer, comprising: providing a data set for singing synthesis containing score data representing a time series of notes, a lyrics data representing words corresponding to the respective notes, the lyrics data indicating phoneme data, providing a singing synthesis database which contains various phoneme data, each phoneme data, representing waveforms of phonemes, judging whether phoneme data, based on which waveform data contained in the data set for singing synthesis is synthesized, is available or not for a user to edit a singing voice, wherein it is judged that the indicated phoneme data is available if the indicated phoneme data is stored in the singing synthesis database which contains various phoneme data; and synthesizing the waveform data while shifting pitches of the indicated phoneme data to pitches indicated by the score data and connecting the pitch-shifted phoneme data, characterized in that, the various phoneme data contained in the singing synthesis database are phoneme data groups each corresponding to a respective tone of voice of a particular person, the singing synthesis database being a set of plural phoneme data groups corresponding to tones of voices of plural persons, respectively, and the indicated phoneme data is judged to be not available, if a phoneme data group corresponding to the indicated phoneme data is not contained in the singing synthesis database, and if the indicated phoneme data is not available, the synthesizing synthesizes new waveform data based on the score data, the lyrics data, and substitute phoneme data available for the user instead of the indicated phoneme data, said substitute phoneme data belonging to a phoneme data group contained in the singing synthesis database. providing a data set for singing synthesis containing score data representing a time series of notes, a lyrics data representing words corresponding to the respective notes, the lyrics data indicating phoneme data, providing a singing synthesis database which contains various phoneme data, each phoneme data, representing waveforms of phonemes, judging whether phoneme data, based on which waveform data contained in the data set for singing synthesis is synthesized, is available or not for a user to edit a singing voice, wherein it is judged that the indicated phoneme data is available if the indicated phoneme data is stored in the singing synthesis database which contains various phoneme data; and synthesizing the waveform data while shifting pitches of the indicated phoneme data to pitches indicated by the score data and connecting the pitch-shifted phoneme data, characterized in that, the various phoneme data contained in the singing synthesis database are phoneme data groups each corresponding to a respective tone of voice of a particular person, the singing synthesis database being a set of plural phoneme data groups corresponding to tones of voices of plural persons, respectively, and the indicated phoneme data is judged to be not available, if a phoneme data group corresponding to the indicated phoneme data is not contained in the singing synthesis database, and if the indicated phoneme data is not available, the synthesizing synthesizes new waveform data based on the score data, the lyrics data, and substitute phoneme data available for the user instead of the indicated phoneme data, said substitute phoneme data belonging to a phoneme data group contained in the singing synthesis database.