3. The method of claim 1 , further comprising: creating an enriched transcription of a run-time text string; using the speech-adapted converted HMM based speech features generator to convert the enriched transcription into corresponding output speech features; and generating a synthesized utterance of the enriched transcription using the output speech features, the synthesized utterance having voice characteristics of the target speaker.
3. The method of claim 1 , further comprising: creating an enriched transcription of a run-time text string; using the speech-adapted converted HMM based speech features generator to convert the enriched transcription into corresponding output speech features; and generating a synthesized utterance of the enriched transcription using the output speech features, the synthesized utterance having voice characteristics of the target speaker. 4. The method of claim 3 , wherein the converted HMM based speech features generator is part of a text-to-speech (TTS) system, wherein creating the enriched transcription of the run-time text string comprises receiving the run-time text string at the TTS system, and converting the received run-time text string into the enriched transcription of the run-time text string by the TTS system, and wherein generating the synthesized utterance of the enriched transcription using the output speech features comprises synthesizing speech by the TTS system.