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Chapter 6 Filter eects 13 4
When combined, Formant Stretch and Formant Shift alter the formant structure of the
resulting vocoder sound, which can lead to interesting timbre changes. For example, using
speech signals and tuning Formant Shift up results in “Mickey Mouse” eects.
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: Use of the Formant Stretch and Formant Shift parameters can result in the generation of
unusual resonant frequencies when high Resonance settings are used.
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Resonance knob: Rotate to change 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.
EVOC 20 TrackOscillator modulation
The parameters in this section control the LFO, which can be used to modulate either the pitch
of the tracking oscillator, thus creating a vibrato, or the Formant Shift parameter of the synthesis
lter bank.
Modulation parameters
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Shift Intensity slider: Drag to set the amount of formant shift modulation by the LFO.
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Pitch Intensity slider: Drag to set the amount of pitch modulation—vibrato—by the LFO.
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Waveform buttons: Click to set the waveform type used by the LFO. You can choose from the
following waveforms:
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Triangle
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Falling and rising sawtooth
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Square up and down around zero (bipolar, good for trills)
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Square up from zero (unipolar, good for changing between two denable pitches)
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Random stepped waveform (S&H)
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Smoothed random waveform
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LFO Rate knob and eld: Rotate to set the speed of modulation. Values to the left are
synchronized with the host application tempo and include bar values, triplet values, and so on.
Values to the right are nonsynchronized, or free, and are displayed in hertz—cycles per second.
Note: The ability to use synchronous bar values could be used to perform a formant shift
every four bars on a cycled one-bar percussion part, for example. Alternatively, you could
perform the same formant shift on every eighth-note triplet within the same part. Either
method can generate interesting results.