Vocoders attempt to impress the harmonic structure of one sound onto another sound. The modulating sound is broken down into a series of frequency bands, and envelope followers measure how strong the content of each band is. A second carrier sound is then sent through a bank of bandpass filters usually tuned to the same as the frequency bands used for the modulator, with the output of their envelope followers controlling the strength of carrier signal allowed to pass through the bandpass filters.
Stepping outside of all that theory, this is how a synth is made to “sing” – a vocal is impressed upon a synth sound (think Mr. Blue Sky and other similar songs). But vocoders can be used in general to create some interesting cross-breeding of sounds. For example, I often use a rhythm track as a modulator and ambience or spoken word as the carrier.« Back to Glossary Index