19. The system of claim 14 , wherein the set of generator-model functions for each given output HMM state model comprises a multivariate spectral probability density function (PDF) for jointly modeling spectral envelope parameters of a phonetic unit of the output language modeled by a given output HMM state model, and a multivariate excitation PDF for jointly modeling excitation parameters of the phonetic unit of the output language, wherein the set of generator-model functions for each given auxiliary HMM state model comprises a multivariate spectral PDF for jointly modeling spectral envelope parameters of a phonetic unit of the input language modeled by the given auxiliary HMM state model, and a multivariate excitation PDF for jointly modeling excitation parameters of the phonetic unit of the input language, and wherein the particular set of generator-model functions from among the auxiliary HMM state models of the second configuration that most closely matches the set of generator-model functions of the given output HMM is the particular set for which: (a) the multivariate spectral PDF is computationally nearest to the multivariate spectral PDF of the given output HMM state model in terms of a distance criterion based on one of mean-squared-error (mse) or Kullback-Leibler distance, and (b) the multivariate excitation PDF is computationally nearest to the multivariate excitation PDF of the given output HMM state model in terms of a distance criterion based on one of mse or Kullback-Leibler distance.
22. The system of claim 19 , wherein the spectral envelope parameters of the phonetic unit of the output language are Mel Cepstral coefficients, Line Spectral Pairs, Linear Predictive coefficients, or Mel-Generalized Cepstral Coefficients, and further include indicia of first and second time derivatives of the spectral envelope parameters of the phonetic unit of the output language, and wherein the spectral envelope parameters of the phonetic unit of the input language are Mel Cepstral coefficients, Line Spectral Pairs, Linear Predictive coefficients, or Mel-Generalized Cepstral Coefficients, and further include indicia of first and second time derivatives of the spectral envelope parameters of the phonetic unit of the input language.