The vocoder relies on two different two different types of sonic inputs. The “carrier wave” could be a clean analog sawtooth wave; a highly-processed, distorted, digital concoction but it’s generally a normal synth sound you trigger by playing notes on a keyboard.The second element is the “modulator”. The microphone is plugged into the vocoder which allows you to play a synthesizer with your fingers and have it sound like it’s speaking or singing.
There are some really good, accessible vocoders out there, so it’s easy to give one a try,” says New York producer and multi-instrumentalist Justin Goldner. He recommends the Korg microKORG and microKORG XL synthesizers, both of which have built-in vocoders.
Read more about this here: http://blog.discmakers.com/2017/11/meet-the-vocoder/