1. A method comprising: detecting incorrect stress patterns in selected acoustic units representing speech to be synthesized; performing a word level analysis of the incorrect stress patterns, a phrase level analysis of the incorrect stress patterns and a sentence level analysis on the incorrect stress patterns to yield analyses, wherein the analyses are performed in parallel; and modifying, via a processor and prior to waveform synthesis, the incorrect stress patterns in the selected acoustic units according to the analyses, to yield corrected stress patterns.