This paper presents an analysis of the rather unusual tone system of the almost totally undocumented Thɔnkɔ /t̪ɔŋkɔ/ dialect of Limba, a Niger-Congo language of Sierra Leone (and slight overlap into Guinée). As we will show, most words are all low tone in their citation form, but exhibit a wide range of tonal contrasts with different high tones popping up when words occur in context. We will illustrate, step by step, how the observed facts justify the proposed contrastive underlying forms and reveal tonal alternations which are best treated with such abstract representations. To show the opaqueness of the widespread tonal neutralization within the system which results from Final High Lowering (FHL), we begin with the interaction of nouns and their adnominal modifiers and then turn to the verb phrase and the clause. We show that the L% boundary tone triggering FHL occurs at the end of declarative and imperative utterances as well as yes-no questions but, interestingly, not at the end of WH questions.
Hyman et al. (Wed,) studied this question.