The development in tone languages of lexically distinct tones out of prior contrasts in voicing. For example, the Southern Kammu language has the words klaang and glaang. Both of these words correspond to klaang in Northern Kammu, but with different tones: the voice contrast has been replaced by a tone contrast: tonogenesis has occurred. Usually voiced obstruents give rise to low tone, and voiceless obstruents give rise to high tone. Other phonation types (e.g. implosives, glottalization) may also give rise to tonogenesis.