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Synonyms for Voice (same or very similar meaning)

WordNet sense 1 (an advocate who represents someone else's policy or purpose):
interpreter, representative, spokesperson

WordNet sense 2 (the sound made by the vibration of vocal folds modified by the resonance of the vocal tract):
vocalization, phonation, vocalisation, vox, vocalism

WordNet sense 3 (expressing in coherent verbal form):

WordNet sense 4 (the melody carried by a particular voice or instrument in polyphonic music):

WordNet sense 5 (utter with vibrating vocal chords):
sound, vocalize, vocalise

From the ODE community, based on WordNetadd/edit