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13 Vocoder—Basics
If you are new to vocoders you should read this chapter.
It provides you with basic knowledge about vocoders and their functionality. You will
also find tips on using vocoders, and achieving good speech intelligibility.
What Is a Vocoder?
The word Vocoder is an abbreviation for VOice enCODER. As with many technologies in
this otherwise beautiful world, it is a child of war. The Vocoder was initially developed
for secure speech transmission over telephone lines which couldn’t be tapped. To
achieve this, the speech signal was analyzed and only the cryptic results of the analysis
were transmitted over telephone lines. On the receiving side, these results were used to
synthetically rebuild the original voice signal.
Fortunately, Vocoders are used nowadays for altogether more peaceful purposes—
namely for music. A Vocoder analyses and transfers the sonic character of the audio
signal arriving at its analysis input to the audio signal present at its synthesis input. The
result of this process is heard at the output of the Vocoder.
The classic vocoder sound uses speech as the analysis signal and a synthesizer sound as
the synthesis signal. This classic sound was popularized in the late 70’s and early 80’s.
You’ll probably know it from tracks such as “O Superman” by Laurie Anderson, “Funky
Town” by Lipps Inc. and numerous Kraftwerk pieces—from “Autobahn” and “Europe
Endless” up to “The Robots” and “Computer World”.
Away from these “singing robot” sounds, vocoding has also been used in many films. As
examples: the Cylons in Battlestar Galactica, and most famously, on the voice of Darth
Vader from the Star Wars saga.
Vocoding, as a process, is not strictly limited to vocal performances. You could use a
drum loop as the analysis signal to shape a string ensemble sound arriving at the
synthesis input.