Voder-vocoder is very old device. Human voice is buzzes and hisses mixed various ways; true even of a coloratura soprano. A vocoder analyzes buzzes and hisses into patterns, one a computer (or trained eye) can read. A voder is a little box which can buzz and hiss and has controls to vary these elements to match those patterns. A human can "play" a voder, producing artificial speech; a properly programmed computer can do it as fast, as easily, as clearly as you can speak.