Vocoder
Last Edited: Dec 24, 2023
Vocoder History
The vocoder (voice coder) is derived from work in the telecommunications field to compress the human voice for more efficient telephone communication. Bell Labs, among other companies, worked on vocoder technology in the 1950s. This involved splitting voice sound into separate frequency bands (as found on the graphical equalizer of hi-fi sound systems) and using the output of each round to drive an amplifier applied to just one frequency band of an alternative input signal. In other words, the incoming voice's tone was superimposed on the pitch and level of a different incoming sound. When this was a simple synthesized drone or buzz, the unexpected effect was that of a "speaking synthesizer." It also took on the exact pitch of the incoming drone.
Vocoder Structure
Regarding its structure, it needs two inputs in musical applications. Usually, the modulator and the carrier are a voice plus a synthesized sound. The performer only has to speak, while playing the keyboard usually determines the melody. The more analysis the filter bands vocoder has, the more intelligible the output sound becomes. In earlier decades of the 20th century, high-quality filters were expensive to build, and so early vocoder designs were extremely costly. Just a couple of filters could create simple voice-like effects. The "Sparky's Magic Piano" used this technique to make a singing piano, with the BBC's Radiophonic Workshop adopting these techniques very early on. Walter Carlos and the TONTO duo created a vocoder-like effect in the early 1970's. However, the German experimental duo Kraftwerk commissioned a full custom vocoder around 1973. It appears on the track Ananas Symphonie on the Ralf and Florian album. Sennheiser in Germany and Harold Bode in the USA, who worked with Robert Moog, also created expensive vocoder designs. After Kraftwerk's worldwide success with the Autobahn album in 1974, they could buy and imaginatively apply these.
Musical Use
It fell out of fashion after finding great use in Techno and Dance music throughout the 1990s. When digital synths such as Yamaha DX7 and Roland D50 largely replaced analog designs, the appearance of new models dried up. It was quickly realized that a digital signal processing intended to create reverb, delay, and other effects could as effectively realize the vocoder effect. So, it reappeared as a gimmicky effect on inexpensive studio rack mounts. Later, analog synths such as Quasimidi, Novation, Korg, or Access appeared. The Access Virus kb became a vocoder of choice for Kral Bartos when he left the Kraftwerk. However, all of these lacked the individual controls of filter bands available on earlier analog designs.
Analog Revival
After the analog revival, some other designs emerged, including simple rack-mounts from MAM, Fat, and the Next. These often included the monophonic sound source enough to reproduce the straightforward "robot voice." This took it back to basics, with separate analysis and synthesis sections, white noise generations, and a module to control hold and other parameters within the vocoder circuit design.
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