16-6
DSP Functions
The DSP Functions
Use bipolar settings for KStart when you want to gradually increase or decrease the key tracking
effect of the currently selected DSP function across the entire keyboard range. With KStart at C 4
bipolar, playing C 4 will apply the DSP function at the level you set with the Adjust parameter,
and will increase or decrease with higher or lower notes, depending on your settings for KeyTrk.
When KeyTrk is set to a negative value, the effect on key tracking is reversed. For keystart
settings above C 4, the effect on key tracking will be maximum at C -1, decreasing with each
note closer to the keystart setting, and remaining constant at and above the keystart setting. For
keystart settings below C 4, the effect on key tracking will be minimum at C 9, increasing with
each note closer to the keystart setting, and remaining constant for notes at and below the
keystart setting.
KStart is available for many of the nonlinear DSP functions, like SHAPER and WRAP. If you
like the control it gives you, you can simulate its effect by using the FUNs. To simulate unipolar
keystart, assign Key Number (KeyNum) as one of the inputs to a FUN, and select one of the
diode equations for the FUN’s Function parameter. To simulate bipolar keystart, assign Bipolar
Key Number (BKeyNum) as one of the inputs of a FUN. Then assign those FUNs to some other
control-source parameter.
The DSP Functions
Filters
Filters are widely used in synthesis to change the timbre of a sound by manipulating the
amplitude of specific partials. When using filters, you always set a reference point (cutoff or
center frequency) that determines which partials the filters affect. Here’s a quick summary of the
effects of the filter functions.
Lowpass filters cut the levels of all partials above the cutoff frequency without affecting the
partials at or below the cutoff frequency (the low frequencies pass through). Highpass filters do
the opposite; they cut the levels of all partials below the cutoff frequency without affecting the
partials at or above the cutoff frequency.
Notch filters, as the name implies, cut the levels of partials in a range between high and low
frequency. Consequently the “cutoff” frequency is referred to as the center frequency. With notch
filters, the levels of partials at the center frequency are cut, while the levels of partials above and
below the center frequency are unaffected. Bandpass filters are the opposite of notch filters; they
leave the levels of partials at the center frequency unchanged, and cut the levels of partials
above and below the center frequency.
One-pole Lowpass One-pole Allpass
Two-pole Lowpass Two-pole Allpass
Two-pole Lowpass, -6 dB resonance Two-pole Notch
Two-pole Lowpass, +12 dB resonance Two-pole Notch, fixed width
Four-pole Lowpass with separation Double Notch with separation
Gated Lowpass Two-pole Bandpass
One-pole Highpass Two-pole Bandpass, fixed width
Two-pole Highpass Twin Peaks Bandpass
Four-pole Highpass with separation
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