Disambiguating Yorùbá tones: At the interface between syntax, morphology, phonology and phonetics

This paper considers a particular type of tonal behavior in Yorùbá with the goal of testing whether syntactic and phonological domains converge or diverge. We consider two types of syntactically conditioned phonological rules: (i) the appearance of phonological elements not present lexically (epenthesis/insertion), (ii) the loss of phonological elements (deletion). These types of rules are often tightly interconnected as the (apparent) loss of one element may involve the appearance of some other element. The cases we consider here involve two Yorùbá tone rules whose surface effect is to change a lexically specified tone (or tone sequence). One of the rules is syntactically conditioned in that it applies across a phrasal boundary; the other rule is morphologically conditioned in that it applies within the word/X0 domain. The two tone rules are conditioned by two distinct domains, namely syntax (the phrasal domain) versus morphology (the word-level domain). We will demonstrate that a consideration of two independent well-formedness conditions—syntactic inclusiveness and phonological structure preservation—leads us to entertain the possibility that the outputs of tone rules will be distinct from one another according to whether they apply across a phrasal domain (i.e. are syntactically conditioned) or whether they apply within a word (i.e. are morphologically conditioned).