Proto-Bantu (PB) is the reconstructed common ancestor of the Bantu languages. Vocabulary is easier to reconstruct than morphology and phonology. However, it is important to try to reconstruct these as well and that was one of the goals of my doctoral research (Goes 2022). While researching the Kikongo Language Cluster (KLC), a language cluster of regional language varieties spoken in four neighboring countries: Angola including Cabinda, the Democratic Republic of the Congo, the Republic of the Congo and Gabon, I aimed to achieve results that also apply to Proto-Bantu. Because of this, a large part of my doctoral research on the language cluster was about vowel harmony. The conclusion is that progressive Vowel Height Harmony (pVAH) involving verbal suffixes cannot be reconstructed to PB nor to the KLC. On the other hand, vowel harmony as part of the wider morphophonology of the Proto-Bantu (PB) verb ending *ide used for the recent past is a much more complex phenomenon. It is certain that the verb ending *ide existed in PB, but in the KLC it shows many different types, so that it was necessary to investigate what the variant was in Proto-Kikongo. Both types of vowel harmony are used in part of the language cluster, as well as in other Bantu languages. But the languages belonging to the KLC stand out because they constitute the only Bantu group that includes languages that lack progressive Vowel Height Harmony but which nevertheless show vowel harmony in the presence of reflexes of the PB verb ending *-ide. Because of this, the KLC is an exceptionally good case for investigating the triggers of this last type of vowel harmony.