This comparative study on the languages of the Congo-Ubangi undertake the documentation, classification and reconstruction of ten Bantu languages (Bolondo, bonyange, Budza language, ebwela, libóbi, lingɔmbɛ, mondongo, monyɔngɔ, mosángé, págáɓéte) spoken in the geographical area between Congo and Ubangi rivers in the north-western of DR Congo and present their interaction with neighboring Ubangian languages (gbánzírí, gɔbú, máɓó, Mbanza, monzɔmbɔ, ngbandi, Ngbaka).
A quantitative lexicostatistic study determines the degree of similarity between the Bantu languages before establishing their phylogenetic classification by integrating our languages into a larger group of 401 Bantu languages illustrated by Neighbor-Net and Neighbor-Joining trees presenting the internal sub-groups of the various groups of Bantu languages generally and the languages of the C area where the Bantu languages of the Congo-Ubangi are particularly classified. Our phylogenetic classification allows visualization of internal relations in C area, which is the first group in the great group of western Bantu languages diverged and which is divided subsequently into three groups.
Phonological description of languages and the study of phonological correspondences related to the proto-Bantu reveal the presence of some foreign phonemes in Proto-Bantu system including implosive and labiovelar stops not as allophones but distinct phonemes of their corresponding explosive velars in several languages. And examining these specific linguistic elements indicates that they would be borrowing from neighboring Ubangian languages.
Overall, it appears that current linguistic features in segmental, suprasegmental (which is not in this study) and structural levels of Bantu languages between Congo-Ubangi would be induced, in part, to contact as much in the past that present with the speakers of non-Bantu languages, especially ubangian languages. However, it would have been an interaction of the Bantu languages with Ubangian languages in light of evidence that we suggest for example, lexical borrowing revealing some direction from Bantu languages to Ubangian languages and other from Ubangian languages to Bantu languages. However, the historical and archaeological evidences on the date and nature of this relationships are low and require interdisciplinary studies in the future.