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• Resonance knob: Resonance is responsible for the basic sonic character of the
vocoder—low settings result in a soft character, whereas high settings lead to a more
snarling, sharp character. Technically, increasing the Resonance value emphasizes the
middle frequency of each frequency band.
Using Formant Stretch and Formant Shift
Formant Stretch and Formant Shift are significant Formant Filter parameters that you can
use separately or in combination (see EVOC 20 TrackOscillator Formant Filter Parameters).
When Formant Stretch is set to 0, the width and distribution of the bands in the Synthesis
filter bank at the bottom matches the width of the bands in the Analysis filter bank at
the top. Low values narrow the width of each band in the Synthesis bank, whereas high
values widen the bands. The control range is expressed as a ratio of the overall bandwidth.
When Formant Shift is set to 0, the positions of the bands in the Synthesis filter bank
match the positions of the bands in the Analysis filter bank. Positive values move the
Synthesis filter bank bands up in frequency, whereas negative values move them down—in
respect to the Analysis filter bank band positions.
When combined, Formant Stretch and Formant Shift alter the formant structure of the
resulting vocoder sound, which can lead to some interesting timbre changes. For example,
using speech signals and tuning Formant Shift up results in “Mickey Mouse” effects.
Formant Stretch and Formant Shift are also useful if the frequency spectrum of the
synthesis signal does not complement the frequency spectrum of the analysis signal. You
could create a synthesis signal in the high frequency range from an analysis signal that
mainly modulates the sound in a lower frequency range, for example.
Note: The use of the Formant Stretch and the Formant Shift parameters can result in the
generation of unusual resonant frequencies, when high Resonance settings are used.
EVOC 20 TrackOscillator Modulation Parameters
The parameters in this section control the LFO, which can be used to modulate either
the frequency—the pitch—of the tracking oscillator, thus creating a vibrato, or the
Formant Shift parameter of the synthesis filter bank.
• Shift Intensity slider: Controls the amount of formant shift modulation by the LFO.
• Pitch Intensity slider: Controls the amount of pitch modulation—vibrato—by the LFO.
117Chapter 6 Filter Effects