Filter And Filter Contour - Moog Minimoog Operation Manual

modifiers
The Modifiers section of the front panel features controls for the two sound modifiers, the
Filter and the Loudness Contour, which respectively shape the overtone content and
loudness/time contour of the audio signal as it passes through the modifying circuitry from
the mixer. In order to hear the effect of these controls, begin by setting the controls in the os-
cillator and mixer sections as follows:
Control
Oscillator MODULATION SWITCH (A)
Oscillator 1 RANGE (4)
Oscillator 1 WAVEFORM (5)
Oscillator 1 VOLUME (12)
Oscillator 1 MIXER switch (C)
Other mixer switches (D, E, F, G)
Switches (J) (K) (L)
The controls on the Modifiers section should still be set as shown in Fig. 1 of the section
titled setting up the instrument.

filter and filter contour

The Mini Moog features a wide-range lowpass filter. This filter attenuates, or cuts out, those
frequency components of an audio signal which lie above a variable cutoff frequency, while
passing those components which lie below it.
1. The CUTOFF FREQUENCY control (17) is used to set the filter's cutoff frequency.
Hold down a key and turn this control first clockwise, then counter-clockwise. You will
hear the tone become more shrill and then more muted, as the higher overtones are first
allowed to pass and then attenuated. If control (17) is moved all the way to the left, the
entire signal will be cut out.
2. The AMOUNT OF CONTOUR control (19) determines the amount of filter contour ap-
plied to the filter's cutoff frequency. Each time a key is depressed, a contour generator
attached to the filter is actuated, and sends a control signal to the filter. The control signal
rises at one rate, then falls at a second rate, and finally levels off at a certain level. This
results in a corresponding rise, fall, and leveling off of the filter cutoff frequency, which
we call the filter contour.
Set the CUTOFF FREQUENCY to -2 and repeatedly depress and hold down a key while
setting the AMOUNT OF CONTOUR at various levels. The more this control is turned
up, the greater will be the increase and decrease in the brightness of each note. Controls
(17) and (19) have an additive effect on the cutoff frequency.
3. The ATTACK TIME control (20) determines the duration of the initial segment of the fil-
ter contour. The initial rise of the filter cutoff frequency can be as short as 10 mil-
liseconds or as long as 10 seconds. (The frequency at which the contour begins is deter-
mined by control (17), while the peak which it reaches is determined by controls (17) and
(19) combined.) Repeatedly depress a key while varying the setting of the ATTACK
Setting
off
16´
narrow rectangular (extreme right)
7
on
off
off