Doepfer A-121 12dB Multimode VCF - Manual (Page 7)

doepfer System A - 100 VCF 2 A-121
7
6. User examples
The A-121’s cut-off frequency can be modulated in a
variety of ways:
• VCF - LFO
Modulation of the cut-off frequency produces cycli-
cal changes of the sound spectrum. At low fre-
quencies (c. 1 - 5 Hz), you get a "Wah-Wah"-
effect. Modulation in the audio range produces
interesting sounds; the same principles apply here
as with frequency modulation of the A-110 VCO
(see chapter 6).
• VCF - ADSR
Modulation by an envelope results in gradual
change of the sound spectrum. Typical uses
would be the synthesis of electric bass or drum
sounds, and filter sweeps, which slowly sweep
through the audio spectrum, emphasising different
harmonics.
• VCF - Keyboard CV
This modulation produces pitch-related filter ope-
ning and closing.
Spatial manipulation of the spectrum
Fig. 3 shows an interesting application of the multi-
mode filter. Each of the four outputs is fed to one
corner of a quadraphonic sound stage (VCAs and
amplifiers, etc. have been omitted for the sake of
clarity).
Each channel sends out only a part of the audio
spectrum, depending on its respective filter’s fre-
quency response, and the result is interesting spatial
distribution of the different spectral elements of the
sound.
Fig. 3: spatial manipulation of the spectrum
Audio
In
FCV 2
FCV 2
QCV 1
QCV 2
QCV 2
Res.
FCV 1
A-121
MULTIMODE
FILTER
Freq.
Audio Level
Low Band High Notch
Quad Space
Input