On pitch lowering not linked to voicing: Nguni and Shona group depressors

This paper tests how well two theories of tone–segment interactions account for the lowering effect of so-called depressor consonants on tone in languages of the Shona and Nguni groups of Southern Bantu. I show that single source theories, which propose that pitch lowering is inextricably linked to consonant voicing, as they are reflexes of the same feature, cannot account for the full range of depressor effects. An Optimal Domains Theory account incorporating grounding constraints to formalize tone–segment feature relations can. One problem these languages pose for single source theories is that some of the depressors are diachronically, as well as synchronically, voiceless. The Appendix establishes this point in detail for the Nguni group.