Programming Examples
Example 2
19-4
Example 2
Lowpass Filter, Envelopes
This example will show you how to assign a DSP function to an algorithm block (the 4-pole
lowpass Þlter), and adjust its control parameters. YouÕll also set up an envelope to control the
cutoff frequency of the Þlter.
Start with Program 199, press EDIT, and select the KEYMAP page (This is explained in a bit
more detail in the previous example, if you havenÕt read it). Change the value to Ò6 Ensemble
Strings.Ó String sounds are especially responsive to lowpass Þltering, because they have a great
deal of activity in the higher frequencies. Lowpass Þlters, depending on their cutoff
frequencies, attenuate high frequencies, so a bit of adjustment can alter a string sound
considerably.
Next, press the ALG soft button to select the ALG page. The center DSP function block will
already be selected. Set its value to Ò4POLE LOWPASS W/ SEP.Ó Notice how the sound
changes. Press the more> soft button, and the three soft buttons that select the control input
pages for the lowpass Þlter will appear. Press the F1 FRQ soft button.
The Coarse Adjust parameter will already be selected. Try a few different values for this
parameter, to get a feel for its effect on the sound. Then set it to a value of G#3 208 Hz (Try
holding down the ENTER button and striking G#3 on your controllerÕs keyboard). Use the
cursor buttons to select the Src1 parameter, and set its value to MPress (3, 3, ENTER). Cursor
down once to the Depth parameter, and set it to a moderate value, like 3800 cents. Now try
playing and applying pressure to the keys. (Obviously, this will have no effect if your MIDI
controller doesnÕt send mono pressure.)
Cursor down to the Src2 parameter, and set its value to ENV2 (1, 2, 1, ENTER). Cursor down to
the DptCtl parameter and set its value to ON. Cursor down to the MaxDpt parameter, and set
its value to 5800 cents. As soon as you set a depth, youÕll hear the envelope sweep the cutoff
frequency. WeÕll adjust it further in a minute. The F1 FRQ page should now look like this:
Edit|Prog:F1|FRQ(4P|LOPASS)|>Layer:1/1||
Coarse:G#3|208Hz|||Src1||:MPress||||||||
Fine||:0ct|||||||||Depth|:3800ct||||||||
|||||||||||||||||||Src2||:ENV2||||||||||
KeyTrk:0ct/key|||||DptCtl:ON||||||||||||
VelTrk:0ct|||||||||MinDpt:0ct|||||||||||
Pad|||:0dB|||||||||MaxDpt:5800ct||||||||
<more||F1|FRQ|F2|RES|F3|SEP|F4|AMP|more>
Next, press the F2 RES soft button to select the page for adjusting the resonance of the lowpass
Þlter. Select the Src1 parameter, and set its value to Data (6, ENTER). Select the Depth
parameter and set its value to 30.0 dB. This means that the partials at the cutoff frequency will
be boosted 30 dB. The F2 RES page should look like the following diagram. If your MIDI
controller has a data slider (or a control that can be programmed to send MIDI 06), the data
slider (or programmable control) will affect the resonance of the Þlter.
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