1. A method of smoothing fundamental frequency discontinuities at boundaries of concatenated speech segments, each speech segment characterized by a segment fundamental frequency contour and including two or more frames, comprising: determining, for each speech segment, a beginning fundamental frequency value and an ending fundamental frequency value; adjusting the fundamental frequency contour of each of the speech segments according to a predetermined function calculated for each particular speech segment, wherein parameters characterizing each predetermined function are selected according to the beginning fundamental frequency value and the ending fundamental frequency value of the corresponding speech segment.