1. A method for generating a frequency warping function, comprising: operating at least one programmed processor to carry outs acts of: identifying occurrences of at least one pair of a phoneme and a context for the phoneme present in training speech for both a source speaker and a target speaker; performing frame alignment on audio data of the training speech for the source speaker and audio data of the training speech for the target speaker corresponding to the occurrences; selecting selected frames from the audio data of the training speech for the source speaker and the audio data of the training speech for the target speaker corresponding to the occurrences; extracting corresponding sets of formant parameters from the selected frames, the extracting comprising: extracting, from one or more first selected frames of the audio data of the training speech for the source speaker that comprise audio of a first phoneme in a first context, a first set of one or more formant parameters of the source speaker for the first phoneme in the first context, extracting, from one or more second selected frames of the audio data of the training speech for the target speaker that comprise audio of the first phoneme in the first context, a second set of one or more formant parameters of the target speaker for the first phoneme in the first context, extracting, from one or more third selected frames of the audio data of the training speech for the source speaker that comprise audio of the first phoneme in a second context, a third set of one or more formant parameters of the source speaker for the first phoneme in the second context, and extracting, from one or more fourth selected frames of the audio data of the training speech for the target speaker that comprise audio of the first phoneme in the second context, a fourth set of one or more formant parameters of the target speaker for the first phoneme in the second context; and generating a frequency warping function based on the corresponding sets of formant parameters, wherein generating the frequency warping function comprises: calculating a first relationship between the first set of one or more formant parameters and the second set of one or more formant parameters, and calculating a second relationship between the third set of one or more formant parameters and the fourth set of one or more formant parameters.