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Vocoder
A vocoder is a device that analyzes the character (the frequency response
of each band) of a “modulator” signal (typically a human voice from a
mic), and applies a filter with the analyzed characteristics to the “carrier”
signal (typically a waveform produced by an oscillator), imposing a vocal
character on that waveform, and making it seem as though the instru-
ment is talking.
As shown in figure 0-2, a vocoder program consists of two signals; a
carrier (the signal that is modified) and a modulator (the signal that
modulates the carrier). These signals are routed to the vocoder section.
Figure 0-2
Timbre 1
Timbre 2
Synth
Audio In 1
Synth
Vocoder
EQ
EQ INSERT FX1/2
INSERT FX1/2
MASTER FX
Audio In 2
Carrier
Modulator
OUTPUT
(L/MONO, R)
Vocoder Sw= ON & Modulator AudioSrc = Timbre2
Vocoder Sw= ON
Pan1…16
Level1…16
ANALYSIS
FILTER
ENVELOPE
FOLLOWER
SYNTHESIS
FILTER
Resonance
Fc Offset
Formant shift
E.F. Sens
Band1
Band16
Audio Input 2
Timbre 1
LEVEL
Modulator
Carrier
LEVEL
Direct
Level
HPF
Level
HPF
Formant Motion
On/Off
Audio Input 1
Timbre 2
FORMANT
MOTION DATA
To Timbre 1 EQ
Vocoder
Vocoder section (VOCODER)
The vocoder divides the audio spectrum into “bands”. In the R3, the
vocoder uses 16 bands. There are actually two sets of 16 bands; the first is
used to analyze the tonal characteristics of one sound (the Modulator),
and the second set is used to apply the same characteristics to another
sound (the Carrier). Each analysis band contains a bandpass filter and an
envelope follower. Each synthesis band contains a band pass filter whose
output is controlled by the matching envelope follower in the analysis
band. The modulator’s audio signal is sent through the sixteen bandpass
filters (the analysis filters), and the envelope follower detects the volume
envelope (change over time) for each of these frequency bands.
The carrier’s audio signal is sent through the other set of sixteen
bandpass filters (the synthesis filters), and the envelope detected from
each analysis filter is applied to each synthesis filter to modulate the
sound, producing the impression that the carrier sound is “talking” (the
typical vocoder effect). You can use the “FrmntSft (formant shift)” and
“FcOffset (Cutoff)” parameters to shift the frequencies of the carrier
bandpass filters. This will raise or lower the frequency response while
preserving the character of the modulator, creating major changes in the
sound.
Modulator (MODULATOR)
Most commonly, you will input your voice as the modulator, but interest-
ing results can also be obtained by inputting a rhythm sound as the
modulator waveform. You can use an Audio Input1, Timbre2 or a
Formant motion data as the modulator.
Carrier (CARRIER)
A sawtooth wave (SAW) or other waveform rich in overtones is the best
choice for the carrier. As the carrier, you can use a combination of two
sources (Timbre1 and Audio Input2).
The structure of a program