Anybody Know Of A Free Vocoder For Mac?

Hey, I'm Really Into Electronic Acoustic, Bands Like: The Secret Handshake, Hello Astronaut, A Rocket To The Moon, And Hellogoodbye. I Make My Own Music But I Just Can't Seem To Find A Free Vocoder To Make My Voice Sound Like Theirs. Anybody Know Of A Free Vocoder For A Mac? Any Suggestions Would Be Helpful, Thanks.