Moog MEMORYMOOG 345 Owner's And Service Manual page 35

THE VOLTAGE-CONTROLLED FILTER
The job of the FILTER is to modify the signals from the sound sources (the OSCILLATORS and the
NOISE SOURCE). The FILTER in the Memorymoog is the patented Moog 24dB/octave lowpass filter.
It's called a lowpass filter because it filters out — stops — high frequencies from getting through and lets
low frequencies pass. The setting of the CUTOFF control (8.2) determines how many high frequencies are
filtered out and how many low frequencies are let through. All of the modulation voltage sources that can
be applied to the filter affect its CUTOFF frequency.
To listen to the effect that changing the CUTOFF frequency has on the timber of the various wave-
shapes, set up this patch starting with a live panel:
HEARING WHAT CHANGING THE CUTOFF FREQUENCY DOES
VOLTAGE CONTROLLED FILTER MIXER
OSCILLATORS
Hee HE
PULSE WIDTH (%)}
5
- CUTOFF EMPHASIS CONTOUR AMOUNT
WAVESHAPE
700 | 15 14 { 3 j
400. \ /-3 soo. \ 18 ML woo is 6
100 6 200 rs
o~?~ Se 207/ @h is ~
1MSEC 10SEC _2MSEC 20SEC
ATTACK
e
FREQUENCY PULSE WIDTH (%)
WAVESHAPE
NY tite
. <3 oy ag | []
N
A
RETURN UNCONDISICNAL KEYBOARD RELEASE
TO ZERO FOLLOW
5 1
Age ie
200 —- ~— 12 2— —s 200—
a] ee "/
oO 10 IMSEC 10SEC 2MSEC 20SEC
ATTACK DECAY SUSTAIN RELEASE
VOLTAGE CONTROLLED AMPLIFIER
FREQUENCY puLse wipti (%)
2MSEC 20SEC
KEYBOARD
=o 10
NOISE
TURN CUTOFF FREQUENCY
SLOWLY, LISTENING TO THE
TONE OF EACH WAVEFORM.
EXPERIMENT WITH CHANGING
WAVESHAPES, CHANGING LEVELS,
CHANGING OCTAVES.
LISTEN TO THE EFFECT
THE CUTOFF FREQUENCY
HAS ON THE NOISE SOURCE.
Play a low note on the keyboard. Slowly turn the CUTOFF control, listening to the harmonics
being swept. You'll notice that if you play high notes and turn the CUTOFF control down too far
(counterclockwise to -3 or - 5) you won't hear any sound at all. That's because the FILTER CUTOFF
is below the frequencies of the note you're playing.
EMPHASIS
Turning this control up puts a resonant peak at the FILTER's CUTOFF frequency. When the setting
is a little past 7, the FILTER actually starts oscillating on its own, becoming another sound source.
Listen to the effect of turning the EMPHASIS control (see diagram on the following page):
31