This thesis studies the interactions of vowel tone with consonantal voice. Briefly, tone-voice interactions refer to: (i) voiced--not voiceless--onsets block high tone spreading; (ii) voiceless--not voiced--onsets block low tone spreading; (iii) sonorant onsets are transparent to both tonal processes. There are many variations to these archetypical patterns of tone-voice interactions. I argue that these variations as well as the archetypical patterns can receive a revealing account from the phonological theory. Specifically, this thesis explores the Prosodic Hypothesis of Tone-Voice, which claims: (i) tone must be represented prosodically (namely, tone is associated to mora); and (ii) tone-voice relations must be expressed by conditions (namely, path conditions, proposed in Archangeli and Pulleyblank (in prep)). By exploiting tonal representations and conditions on tone-voice, the Prosodic Hypothesis provides a principled account of tone-voice in Ngizim, Ewe, and Nupe. The result is a principled theory that unifies the known phonetic and phonological facts about tone-voice and that makes testable predictions about the nature and type of expected tone-voice interactions. In addition to tone-voice, this thesis investigates a range of theoretical issues from tonal representations, to onset representations, to the privative voicing theory to Grounded Phonology (Archangeli and Pulleyblank in prep.). I demonstrate that detailed formal analyses of tone-voice can not only uncover facts about tone-voice, but can also make important contributions to phonological theory.