Hi, Marvin,
I have worked on Syllable HMM based Mandarin TTS before. It is not very difficult for Mandarin since the number of syllables in Mandarin is quite limited. Below is my paper published in Interspeech 2009.
Z. Shuang, S. Kang, Q. Shi, Y. Qin, and L. Cai, Syllable HMM based Mandarin TTS and comparison with concatenative TTS. ;In Proceedings of INTERSPEECH. 2009, 1767-1770.
Zhiwei Shuang------------------ Original ------------------From: "Marvin Coto"<mcotoj@xxxxxxxxx>;Date: Thu, Jul 18, 2013 10:49 PMTo: "hts-users"<hts-users@xxxxxxxxxxxxxxx>;Subject: [hts-users:03819] Synthesis by syllablesHello! I would like to know if somebody has research on speech synthesis by syllables instead of phonemes, and how difficult would it be to implement in HTS.