24
Filter
Sequential
3. Return the cutoff knob to its halfway position, hold down a note again
then turn the resonance knob about halfway up.
4. Rotate the lter’s cutoff knob again and listen to the sound change as a
band of frequencies near the cutoff is amplied.
5. Now toggle between the lters by pressing the rev switch and listen
to the differences in tone. The differences become more apparent with
higher and lower resonance settings.
In the previous examples, you controlled the lter cutoff by hand. In
most cases, you will use the Filter Envelope to do this. To learn more
about the Filter Envelope see page 25.
Filter Controls
Rev Switch: 1/2, 3—This selects the lter type. The Rev 1/2 lter is a
SSI 2140 low-pass, 4-pole, 24 dB per-octave resonant lter. The Rev 3
lter is a Curtis CEM 3320 low-pass, 4-pole, 24 dB per-octave resonant
lter. Both lters can self-oscillate when resonance is set to its maximum.
Cutoff: 0...10—Sets the lter’s cutoff frequency.
Resonance: 0...10—Emphasizes a narrow band of frequencies around
the cutoff frequency. High levels of resonance can cause either lter to
self-oscillate and generate its own pitch.
Envelope Amount: 0...10—Sets the amount of modulation from the
lter envelope to the lter’s cutoff frequency. Any setting above zero
means that each time you strike a key, the lter envelope controls how
the lter opens and closes. Higher amounts more dramatically affect the
cutoff frequency.
Keyboard: off, half, full—Sets the amount of modulation from the
keyboard to the lter’s cutoff frequency. Selecting half or full means
that the higher the note played on the keyboard, the more the lter opens.
This is useful for adding brightness to a sound as higher notes are played,
which is typically how acoustic instruments behave. If both half and full
are off, keyboard lter tracking is off, meaning that lter frequency is unaf-
fected by playing higher or lower notes on the keyboard.
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