Consonant-tone interactions in Gengbe

Gengbe is an under-documented and understudied Gbe language spoken as a lingua franca in Southern Togo and Benin. Few resources for Gengbe exist, especially in the domain of empirical acoustic phonetic research. To this end, we present an overview of its consonant, vowel, and tonal inventories. Of particular interest is the fact that its two register tones, (L)ow and (H)igh, show systematic phonological variation based on the voicing of onset consonants. Like many other tone languages in Africa and beyond, voiced obstruents act as so-called “depressor consonants,” triggering lower f0 on subsequent vowels than do their voiceless counterparts. This lowering is phonologized in many H tone contexts, resulting in a Rising tone in many (but not all) morphophonological environments. The distinction is phonetically present in low tone as well, where it perseverates across the entire vowel and results in a lower register L (by approx. 20 Hz). We survey the phonological environments where such lowering effects are realized, and probe the interaction between obstruent voicing, tone, vowel height, and nasality via instrumental acoustic analysis.