A unified account of grammatical tone and length in Gã

In Gã [Kwa: Ghana], several aspectual and modal distinctions are exponed through changes in tone. These grammatical tones may be realized on a subject proclitic, or on a verbal prefix when the subject is not pronominal. Previous analyses of this phenomenon have differed in the representation of the underlying forms: in particular, whether the alternations are suppletive or the result of predictable phonological processes has been a point of discussion. In this paper, I present novel data which sheds light on these processes and propose that the emergence of portmanteau STAMP (Subject, Tense, Aspect, Mood, Polarity) morphs in Gã is fully predictable from regular phonological processes present in the language, including independently motivated vowel hiatus resolution strategies, syllable structure restrictions, and tone association rules. I argue that the STAMP morphs in Gã are best analyzed as derived phonologically from combinations of individual underlying items, where each morphosyntactic feature contributes a distinct phonological component. This analysis is able to account for grammatical distinctions which involve changes in vowel length as well as tone.