8

Chapter 6 Filter 81
 Frequency bar and fields: The blue bar above the upper row of faders controls the
upper and lower frequencies for both filter banks. Drag the bar to move both the
upper and lower frequencies, drag the left end to move only the lower frequency
(the value range is 75 to 750 Hz), or drag the right end to move only the upper
frequency (the value range is 800 to 8000 Hz). You can also edit the numerical values
above the bar directly (between 80 and 8000 Hz).
 Lowest button: Sets whether the lowest band of each filter bank acts as a lowpass or
bandpass filter.
 Highest button: Sets whether the lowest band of each filter bank acts as a highpass
or bandpass filter.
 Formant Stretch knob: Alters the width and distribution of the bands in the synthesis
filter bank, extending or narrowing the frequency range defined by the blue bar
(Low/High frequency parameters) for the synthesis filter bank.
If Formant Stretch is set to 0, the width and distribution of the bands in the synthesis
filter bank is equal to the width of the bands in the analysis filter bank. Low values
narrow the width of each band, while high values widen it. The control range is from
0.5 to 2 (as a ratio of the overall bandwidth).
Note: You can jump directly to a value of 1 by clicking on its number.
 Formant Shift knob: Shifts the position of the bands in the synthesis filter bank up or
down. When set to 0, the position of the bands in the synthesis filter bank is equal to
the position of the bands in the analysis filter bank. Positive values will move the
bands up in frequency, while negative values will move them down in respect to the
analysis filter bank. You can jump directly to the values –0.5, –1, 0, +0.5 and +1 by
clicking on their numbers.
∏ Tip: When combined, Formant Stretch and Formant Shift alter the formant structure of
the resulting vocoder sound, and can result in some interesting timbre changes. As an
example, using speech signals and tuning Formant Shift up results in Mickey Mouse
effects. Formant Stretch and Formant Shift are especially 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 which mainly modulates the sound in a lower frequency range, for
example.
 Resonance knob: Controls the basic sonic character of both filter banks. Increasing
the Resonance emphasizes the middle frequency of each band. Low settings give a
softer character, while high settings give a sharper character.
Note: The use of either, or both, of the Formant Stretch and Formant Shift
parameters can result in the generation of unusual resonant frequencies when high
Resonance settings are used.