What is another word for "mouthpiece"?

Roget's Thesaurus (1911) lists these synonyms for "mouthpiece": annotator, cicerone, commentator, courier, demonstrator, dragoman, explainer, exponent, expositor, expounder, glossarist, interpreter, metaphrast, oneirocritic, oracle, paraphrast, place, prolocutor, scholiast, showman, speaker, spokesman, valet.