[kp] is rare in Tuki, only three examples in basic nouns and verbs are found in the corpus: ʊ̀≠kpá utter (incantations); ɪ̀≠kpáá forest and ʊ̀≠kpátá black ant sp.
 [gb] and [ŋmgb] are also rare in Tuki. The only examples found in the corpus are: ì≠ŋᵐgbə́mə́ lion, ŋm≠gbə́ɾə́ witchcraft, ŋm≠gbì pipe (tobacco), and ʊ̀ŋm≠gbɔ̌k-ɔ́ŋ-ɔ́ calamity.
 In most of the previous studies, Tuki is analysed as having a seven-vowel inventory, such as /i, e, ɛ, a, ɔ, o, u/ (Biloa 1997) or /i, e, ə, a, ɔ, o, u/ (Hyman 1980, for the dialect Tocenga); or as having a six-vowel inventory /i, e, a, ɔ, o, u/ as in Kongne Welaze (2004) and Essono (1972) ‑‑although in Essono (1980) the front mid vowel is identified as an archiphoneme E. I propose a different interpretation of "e". As Tuki shows evidence of ATR harmony and the vowel commonly written as "e" shows evidence of behaving in some contexts as a [+ATR] vowel and in other contexts as a [‑ATR] vowel, I have chosen to reinterpret the [‑ATR] vowel as /ɪ/ and the [+ATR] vowel as [e], which, despite its high F2, is most likely underlyingly /ə/. The behaviour of these vowels will be discussed in depth below.
 While most seven-vowel systems have either /i, ɪ, ɛ, a, ɔ, ʊ, u/ or /i, e, ɛ, a, ɔ, o, u/ inventories, many Mbam languages have atypical vowel inventories, often with the lack of both /e/and /ɛ/. In such cases /ə/ is often slightly fronted.