1. A computer-readable memory storing computer-executable instructions that, when executed, cause one or more processors to perform acts comprising: performing formant-based frequency warping on fundamental frequencies and linear predictive coding (LPC) spectrums of source speech waveforms in a first language to produce transformed fundamental frequencies and transformed LPC spectrums; generating warped parameter trajectories based at least on the transformed fundamental frequencies and the transformed LPC spectrums; and producing transformed target speech waveforms with voice characteristics of the first language that retain at least some voice characteristics of a target speaker using the warped parameter trajectories and features from target speech waveforms of the target speaker in a second language.
6. The computer-readable memory of claim 1 , further comprising instructions that, when executed, cause the one or more processors to perform an act of extracting the features that include fundamental frequencies, LSPs, and gains from the target speech waveforms.