A vocoder or a voice coder usually compresses the human voice in a way in which it becomes more efficient when transmitted over the phone. People have used this technology for the course of many years. At first, it involved the splitting of voice sounds into separate frequency bands. After this, it involved the using the output of each band to drive an amp applied to only one frequency band of an alternative input signal.

Vocoders: Inputs

Vocoders need two inputs: a voice plus or modulator and a synthesized sound or carrier. While the performer speaks, the keyboard determines the melody. When the vocoder has more filter bands, the sound becomes clearer. The first high-quality filters and vocoders were quite expensive. Sparky’s Magic Piano was one of the first children’s audio stories that used this technique to create a singing piano. BBC’s Radiophonic Workshop adopted these techniques after that.

Examples of Vocoder-like Effects

Over time, there were many successful attempts to create vocoder-like effects. Some examples include Walter Carlos and the TONTO duo, the German experimental duo Kraftwerk, and Ananas Symphonie’s Ralf and Florian album. Years later, there were the Sennheiser in Germany and Harold Bode in the United States. This last one was done in collaboration with Robert Moog and created high-cost vocoder designs.

Digital Synthesizers vs Vocoder

The vocoder was popular in techno and dance music around 1990. However, soon after, when digital synthesizers took over analog synths, they became obsolete. Examples of digital synths include Roland D50 and Yamaha DX7. Producers and sound engineers realized that a digital signal could create reverb, delay, and other effects that could effectively replace the vocoder one. Not long after, analog synths such as Quasimidi, Novation, Korg and Access appeared. Regardless, all of these lacked the individual controls of filter bands that were included in analog designs. 

Analog synths improved significantly, which led to new vocoder designs. These new designs included a monophonic sound source that was capable of reproducing a robot voice. This was a great discovery that led to many changes regarding the vocoder circuit design.