Basaa language

Basaa (also spelled "Bassa, Basa, Bissa"), or Mbene, is a Bantu language spoken in Cameroon by the Basaa people. It is spoken by about 300,000 people in the Centre and Littoral regions.
Maho (2009) lists North and South Kogo as dialects.
Phonology.
Tone.
Basaa contrasts four tones: high, low, high-to-low (falling) and low-to-high (rising).
Orthography.
The language uses a Latin-based alphabet, with the addition of the letters Ɓɓ, Ɛɛ, Ŋŋ, Ɔɔ, ten multigraphs, as well as acute, grave, and circumflex accents:
Macron and caron diacritics may be used for marking tone in reference works, for example the dictionary by Pierre Emmanuel Njock.