19. The device of claim 15 , wherein the concatenation features of the first speech sound include one or more of a last Fundamental Frequency value (F0), at least one frame of a spectral representation of a beginning portion of the first speech sound, or at least one frame of a spectral representation of an ending portion of the first speech sound.
20. The device of claim 19 , wherein the first speech sound is indicative of a pronunciation of a diphone, wherein the concatenation features of the first speech sound include one or more of a duration of the pronunciation of a first half of the diphone, a duration of the pronunciation of a second half of the diphone, F0 of the pronunciation of the first half of the diphone, F0 of the pronunciation of a center portion of the diphone, or F0 of the pronunciation of the second half of the diphone.