Sequential Prophet VS - Resonance

56
When the keyboard modulation source amount is above 55, “overtracking”
occurs. That is, higher notes are relatively brighter. Similarly, when the
keyboard source amount is below 50, higher notes are relatively duller.
For any keyboard scaling, the lter cuto pivots around the F#3 key. When
the keyboard modulation source is set negative, the lter cuto increases with
lower notes, and decreases with higher notes.
For the broadest lter sweeps, when using a positive Env Amount value, lower
Cuto. When using a negative Env Amount value, increase Cuto.
Since this is a four-pole low-pass lter, the higher-frequency components
of the oscillator mixture (that is, all those above the cuto frequency) are
suppressed at a rate of 24 dB of attenuation per octave. In other words, the
harmonic that is one octave above the cuto frequency is attenuated 24 dB
with respect to the cuto frequency. (This is a sharper lter response than, say,
12 dB/octave.)
Besides cuto, the other lter adjustment which is critical to timbre is
resonance.
RESONANCE
To set lter resonance, press Resonance and use the slider (00-99). The lters
begin to oscillate when the value is approximately 70.
Resonance is the only resonance control. When resonance is low, the
lter has its standard response. As resonance increases, all lter eects
are heightened or accentuated as the lter response curve becomes more
complex. Frequencies below cuto are suppressed while frequencies near
cuto are actually amplied. If the cuto frequency is then modulated, this
resonating lter sweeps across the harmonically-rich input, accentuating those
harmonics near the (varying) cuto frequency. This is a practical way to bring
out a specic range of overtones or replicate certain physical resonances of
acoustic instruments.
When resonance is set very high, the lter can be used as a sine-wave audio
source. This will typically produce a howl or whistling. The exact resonance
point may vary slightly from voice to voice. The pitch of this resonating
oscillation is determined by the lter cuto frequency (as modulated by all
its controllers). The resonating waveshape is a sine wave because only one
frequency (namely, cuto) is present.
Filters operate in part by shifting the phase of their input signals. The amount
of phase shift changes with frequency. To the extent that resonance is
raised, LFO-modulation of the cuto frequency can impose an actual vibrato
(frequency shift) on the audio path because of the resulting phase shift.
Another technique for applying lter phase properties is more appropriate for
complex sounds. When lter resonance is high, the input signal will tend to
synchronize the lter frequency to itself or to a harmonic. If then only the input
signal to the resonating lter is shifted through modulation, the resonant lter
will not change frequency, but will shift phase, producing a harmonic sweep.
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