Tone Sandhi Rules

• All the words change tone unless it is the last word of a sentence or before a comma.
  e.g. Lie karm u pid? U, goar u cidky.

• Vocabularies with backquote (e.g. aang`ee) follow back quote's rule:

  No tones change for the word before backquote. Instead, the syllables after backquote changed to shorter and softer tones.

• Generally, nouns (include gerunds) do not change tone, unless it is used as an adjective, or measure word denoting a unit(e.g.: Taioaan-laang, cidky pid).

  For TTS, this appears to be the biggest challenge. Using POST (part of speech tagging - lexical category) would help. But this is a huge task.
  What are the existing databases out there? What models have been developed for tagging Taiwanese? Can we revise the existing POST for a jump start?
  Further, a vocabulary could be a noun or a verb. How could TTS distinguish the difference when a word has multiple tags?

  Meta's M2M uses different approach to solve complex tone sandhi probelms. Meta’s new AI-powered speech translation system presents a new approach for an unwritten language which is promising.

  Note: MTL vocabularies, like English, may contain muti-syllables . The majority of Taiwanese vocabularies are 2-syllable words. The front syllables may be derived from a syllable which changes the tone based tone sandhi rule. But as a whole, when it is used as a noun, we don't perform any further tone change. Many words contain 'ar' at the end. When creating a word with 'ar', the front syllable will change tone. E.g "niaw" -> "niau'ar" (kitty cat). But if the front syllable is a flat tone, it does not change tone when follows with 'ar'. E.g. "te" -> "te'ar" (bag).

  N	Noun
  C	Conjunction
  r	Pronoun
  

• Pronouns do change tone (goar, lie), unless specifically put a pause during speaking. (eg. emphasizing 'I': goar)

• Demonstrative adverbs/pronouns that have no tone changes are: ciaf, hiaf, cit'ee, hit'ee Note:
  Cit'niar si oseg`ee. where cit'niar does not change tone.

  Cit'niar oseg`ee cyn suie. where cit'niar is an ajective, hence it does change tone.

• Interrogative pronouns that have no tone changes are: tangsii, symmih, uixhøo

• Conjunctions don't change tone are : citmar, tvaf, pwntea, afnny

• Words before conjunctions that don't change tone: A'Efng gaau køq kutlat. where 'gaau' does not change tone.

• Adjectives before 'ee' don't change tone: e.g. byle ee koniuu (vs. suie koniuu, where suie changes tone)

• Functional word - ka: When it is followed by verb, no tone changes.

  Goar ka korng.

  Goar ka y korng. - but this one does change tone.

• Some phrases with parallel structure (verb object, verb object), there is no tone changes for the front vocabulary:

  
  e.g. phaotee khaikarng
       kofng'oe sngroe
       iusafn oansuie
       kekef hoxho
       hongthor binzeeng
       pexlau kviafiux
       lily laklag
  
  The following do change tones, since the nouns are used as adjectives:
  
  e.g: tikhaf-mixsvoax
       zekpeq-hviati
  
  

• Checkout this verb zhwlie in the following two senenteces. In the 1st sentences, it change tones, but it does not in the 2nd sentence.
  MTL ti zengphvi-bwym hongbin, zhwlie kaq cyn suykhuix.
  
  Iong MTL laai zhwlie khaq ittix.
  

• Words that never changed tone