1. A method for use in a Concatenative Text-To-Speech (CTTS) system that comprises a speech segment database comprising a plurality of speech segments organized in accordance with a context hierarchy, the method comprising: evaluating the context hierarchy by using new text and at least one processor, wherein the context hierarchy comprises a plurality of contexts determined using a base text, wherein each of the plurality of speech segments is associated with at least one of the plurality of contexts in the context hierarchy, and wherein the new text is different from the base text, wherein at least a portion of the new text has no corresponding acoustic data used during the evaluation; updating the context hierarchy, based on results of evaluating the context hierarchy by using the new text, by merging two contexts in the context hierarchy to form a new coarser context and/or by splitting a context in the context hierarchy to form at least two new refined contexts; and reorganizing the plurality of speech segments in accordance with the updated context hierarchy.