Phonologists have noted in a number of African language families the occurrence of certain consonants that influence tonal behavior. However, this phenomenon has never been noted in the Voltaic family. In this paper, the author contrasts three varieties of Dagara-Wule, Lobr, and Blrfmr-spoken in southern Burkina Faso and northern Ghana, demonstrating that certain consonants in Wule and Lobr are "transparent", permiting the spread of high tones, while others are "opaque", blocking the spread of high tones.