With a name created by combining voice and encoder into one title, a vocoder is a device that is designed to analyze speech and synthesize it for communication purposes. Developed as a tool for use in telecommunications functions during the 1930s, the main purpose of the vocoder was to code speech for mass transmission. The dual function of the vocoder as both speech analyzer and a voice synthesizer allowed for a more precise means of encrypting the sound for broadcast over radio.
A vocoder operates on the same principles that help to create the production of the human voice. Just as the sound is created by the opening and closing of the glottis in the vocal cords, then filtering the sound through the nose and throat, the vocoder works on a principle of producing a sound that is identified as the fundamental frequency. The frequency is then filtered in a way that produces a range of sounds that elevate the subtle nuances of the fundamental frequency so that the pitch and tone produced are clear and concise.
The earliest vocoders were developed as analog devices which were capable of transmitting on several different radio frequencies, using a series of band pass filters. Initial experiments with the concept of the voder or vocoder began at Bell Labs during 1928, with the first patents filed in 1935. While the initial function of voders had to do with radio transmissions, it was only a matter of time before vocoders found use in private types of communication as well, especially secure military communications during World War II.
Over time, the use of a vocoder spread beyond simple radio communications. Early developments in the new medium of television found value in the basic principles behind vocoder technology, and the movie industry also found applications that aided in the production of ancillary products that could be used to promote new releases.
During the latter part of the 20th century, the vocoder began to make its way into the recording studio with a number of popular artists. Instead of relying on voice as the fundamental component that feeds into the vocoder, musical instruments were used instead. The technology associated with the vocoder progressed from analog sound production to the more sensitive digital sound, which helped to make the vocoder an ideal choice for creating soundtracks for movies, television shows, and enhancing live stage performances.