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Weapon of Choice: Vocoder
A
vocoder (name derived from voice encoder, formerly also called voder)
is a speech analyzer and synthesizer. It was originally developed
as a speech coder for telecommunications applications in the 1930s,
the idea being to code speech for transmission. Its primary use
in this fashion is for secure radio communication, where voice has
to be digitized, encrypted and then transmitted on a narrow, voice-bandwidth
channel. The vocoder has also been used extensively as an electronic
musical instrument.
Vocoder theory
The human voice consists of sounds generated by the opening and
closing of the glottis by the vocal cords, which produces a periodic
waveform with many harmonics. This basic sound is then filtered
by the nose and throat (a complicated resonant piping system) to
produce differences in harmonic content (formants) in a controlled
way, creating the wide variety of sounds used in speech. There is
another set of sounds, known as the unvoiced and plosive sounds,
which are not modified by the mouth in the same fashion.
The vocoder examines speech by finding this basic carrier wave,
which is at the fundamental frequency, and measuring how its spectral
characteristics are changed over time by recording someone speaking.
This results in a series of numbers representing these modified
frequencies at any particular time as the user speaks. In doing
so, the vocoder dramatically reduces the amount of information needed
to store speech, from a complete recording to a series of numbers.
To recreate speech, the vocoder simply reverses the process, creating
the fundamental frequency in an oscillator, then passing it through
a stage that filters the frequency content based on the originally
recorded series of numbers.
Follow
this link to hear a great vocoder demonstration:
keyboardmuseum
Musical applications
For musical applications, a source of musical sounds is used as
the carrier, instead of extracting the fundamental frequency. For
instance, one could use the sound of a guitar as the input to the
filter bank, a technique that became popular in the 1970s.
Musical history
In 1970, electronic music pioneers Wendy Carlos
and Robert Moog developed one of the first truly
musical vocoders. A 10-band device inspired by the vocoder designs
of Homer Dudley, it was originally called a spectrum encoder-decoder,
and later referred to simply as a vocoder. The carrier signal came
from a Moog modular synthesizer, and the modulator from a microphone
input. The output of the 10-band vocoder was fairly intelligible,
but relied on specially articulated speech. Later improved vocoders
use a high-pass filter to let some sibilance through from the microphone;
this ruins the device for its original speech-coding application,
but it makes the "talking synthesizer" effect much more
intelligible.
Carlos' and Moog's vocoder was featured in several recordings, including
the soundtrack to Stanley Kubrick's A Clockwork Orange, in which
the vocoder sang the vocal part of Beethoven's Ninth Symphony. Also
featured in the soundtrack was a piece called "Timesteps,"
which featured the vocoder in two sections. Originally, "Timesteps"
was intended as merely an introduction to vocoders for the "timid
listener", but Kubrick chose to include the piece on the soundtrack,
much to the surprise of Wendy Carlos.
In the late 1970s, vocoder began to appear in pop music, for example
on disco recordings. A typical example is Giorgio Moroder's 1977
album From Here to Eternity. Vocoders are often used to create the
sound of a robot talking, as in the Styx song "Mr.
Roboto". It was also used for the introduction to
the Main Street Electrical Parade at Disneyland.
Vocoder has appeared on pop recordings from time to time ever since,
but in most of cases vocoder works just as a some kind of special
effect in pop music. However, many experimental electronic artists
and representors of "new age" genre often utilize vocoder
in a more comprehensive manner. Jean Michel Jarre
(album Zoolook, 1984) and Mike Oldfield (album Five Miles Out, 1982)
are good examples. There are also some artists who have made vocoder
an essential part of their music. Those include the famous German
group, Kraftwerk, jazz/fusion keyboardist Herbie
Hancock during his late 1970s disco period, Patrick Cowley's
late recordings and more recently, avant-garde-pop group Trans Am.
The song "O Superman" by avant-garde musician,
Laurie Anderson, is a popular recording released in 1981
that incorporates the vocoder. The KLF used vocoder-distorted voices
in their 1991 "Stadium House" mix Last Train to Trancentral
(Live from the Lost Continent). In 1998, Marilyn Manson
utilized the vocoder heavily in their glam- and 70s-influenced LP,
Mechanical Animals, whereon such songs as "User
Friendly" and "Posthuman" among others make substantial
use of the technology. Since 1998, Manson has favored the live concert
use of vocoders and many concert-goers can hear him use the technology
when performing many songs, notably, "Antichrist Superstar".
The bands The Faint, Air, Ween, and Death From Above 1979 all have
extensive use of the vocoder. Daron Malakian, guitarist of System
of a Down has used a Vocoder in the songs, Sugar, War?,
and Old School Hollywood. Muse used a vocoder on
their latest album, Black Holes and Revelations, most notably on
the song "Supermassive Black Hole".
-- courtesy of wikipedia
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