Synthesis of prosody using multi-level unit sequences

Both methods are based on the following procedure. In a recorded, prosodically and phonemically labeled corpus, the log pitch contours are additively decomposed into component curves according to a prosodic hierarchy, typically phrase curves (corresponding to phrases), accent curves (corresponding to feet), and segmental perturbation (or residuals) curves. During synthesis, the corpus is searched for multiple unit sequences: A unit sequence that covers the target phoneme string, and one or more unit sequences that cover the prosodic labels at a given phonological level (e.g., the foot or phrase) and are constrained by being matched to the phone match sequence in terms of the phonetic classes of the phonemes (or in terms of higher level entities, such as the number of feet and their sizes measured in syllables). The methods differ in terms of the level of detail of these constraints. A superpositional prosody transplant procedure generates a target pitch contour by extracting and recombining component curves from these sequences, and imposing this contour on the sequence that matches the phone string using standard speech modification methods. This process minimizes prosodic modification artifacts, optimizes the naturalness of the target pitch contour, yet avoids the combinatorial explosion of standard unit selection synthesis.