Linguistic diversity is disappearing (almost) as fast as biological diversity: very soon, we may no longer be able to know the sounds of many languages still spoken today. Alongside other forms of enquiry, phonetic documentation is thus essential if we are to preserve this disappearing heritage, and learn more about our own linguistic and cognitive evolution. This is particularly crucial in those areas of the world where language density is higher, such as the Democratic Republic of the Congo (henceforth, DRC). Therefore, the first focus of my research is to document the sounds of the “vanishing voices” of the last hunter-gatherer communities of the Upper Kasai Region of the DRC. The region of these groups, commonly known as “Batwa” or “Pygmy”, is one of the least well-surveyed ones of the planet, and language loss there happens at a particularly fast pace. Without the linguistic evidence that those areas can provide, we will lose essential insights into our linguistic history, as well as the peopling dynamics of Central Africa. Historically, the so-called “Bantu Expansion”, i.e. the southward and eastward spread of Bantu-speaking groups over large parts of sub-Saharan Africa, resulted in the disappearance of pre-existing languages in Central Africa. “Pygmies”, in particular, while retaining their genetic and cultural identity, have shifted from their ancestral languages to those of the newcomers. Hence, the second focus of my research: the contrastive study of “Batwa” and “non-Batwa” Bantu language varieties, and the (socio-)phonetic analysis of their possibly different phonological systems, will contribute to the historical appreciation of the striking mismatch we witness in the tropical rainforest between genetics and linguistics.