 A depressor has no effect on a syllable that's already low, but it blocks assimilation to a preceding high tone, so that the tone of the depressor syllable and any following low-tone syllables stays low.Prenasalisation occurs whenever a consonant is preceded by a homorganic nasal, either lexically or as a consequence of prefixation.The most notable case of the latter is the class 9 noun prefix "in-", which ends in a homorganic nasal.