The Dsp Functions; Filters - Kurzweil K2600 Musician's Manual

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 FUNÕs 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

One-pole Lowpass
Two-pole Lowpass
Two-pole Lowpass, -6 dB resonance
Two-pole Lowpass, +12 dB resonance
Four-pole Lowpass with separation
Gated Lowpass
One-pole Highpass
Two-pole Highpass
Four-pole Highpass with separation
Filters are widely used in synthesis to change the timbre of a sound by manipulating the
amplitude of speciÞc partials. When using Þlters, you always set a reference point (cutoff or
center frequency) that determines which partials the Þlters affect. HereÕs a quick summary of the
effects of the Þlter functions.
Lowpass Þlters 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 Þlters 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 Þlters, as the name implies, cut the levels of partials in a range between high and low
frequency. Consequently the ÒcutoffÓ frequency is referred to as the center frequency. With notch
Þlters, the levels of partials at the center frequency are cut, while the levels of partials above and
below the center frequency are unaffected. Bandpass Þlters are the opposite of notch Þlters; they
leave the levels of partials at the center frequency unchanged, and cut the levels of partials
above and below the center frequency.
16-6
One-pole Allpass
Two-pole Allpass
Two-pole Notch
Two-pole Notch, fixed width
Double Notch with separation
Two-pole Bandpass
Two-pole Bandpass, fixed width
Twin Peaks Bandpass