Abstract In this paper, I provide a first systematic analysis of grammatical tone (GT) in the verb phrase of northwestern (NW) Bantu languages. Based on a sample of twelve languages, I show that GT on preverbal subject agreement, tense, aspect, mood, and polarity markers, on the verb stem, and tonal phrase-medial/phrase-final verb distinctions are inherited features. In contrast, GT on elements immediately following the verb is an innovation in some genealogical subgroups of NW Bantu. In Proto-NW-Bantu, GT generally co-occurred with segmental morphemes. This “co-exponence” type is retained in the Proto-B clade of NW Bantu, while languages of Proto-A innovated more exponence types, namely tone-only and segment-only exponents, synchronically exhibiting all three exponence types in individual languages.
Nadine Grimm (Tue,) studied this question.