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Low Frequency Oscillators (LFOs)
A Low Frequency Oscillator or LFO is simply a wave which repeats at a slow rate. The
Proteus has two multi-wave LFOs for each channel. The LFO waveforms are shown in
the following illustration.
R and om
Sq u ar e
12% P u ls e
P at : N eener
C
A#
G
H em i- q uaver
By examining the diagram of the LFO waveforms, you can see how the LFO will affect a
modulation destination. Suppose we are modulating the pitch of an instrument. The
sine wave looks smooth, and will smoothly change the pitch. The square wave changes
abruptly, and will abruptly change the pitch from one pitch to another. The sawtooth
wave smoothly decreases, then abruptly changes back up. The sound's pitch will follow
the same course. Controlling the pitch of an instrument is an easy way to hear the effects
of the LFO waves.
Like the Auxiliary Envelope, the LFOs can be routed to control any realtime functions
such as Pitch, Filter, Panning, or Volume. A common use for the LFO is to control the
pitch of the sound (LFO -> Pitch). This effect is called vibrato and is an important
performance parameter. Many presets use this routing with the modulation wheel
controlling "how much" LFO modulation is applied. Another common effect, Tremolo,
is created by controlling the volume of a sound with the LFO (LFO -> Volume).
Another use for the LFOs might be to add a slight bit of animation to the sound
by routing the LFO to control the filter. In this example, the LFO amount would
be set low, for a subtle effect.
Sa wt oot h
E-MU Systems
Tri a n gl e
Sawto o th
33 % P ul se
2 5% P ulse
P a t: O cta ve s
P a t: Fi f th+ Octa v e
+ Octave
G
C
- Octave
Si n e 1 ,2
Si n e 1 ,3,5
N e g a t i v e A m o u n t
-
+
Sine
16% P ulse
Pat : Sus4 tri p
C
F
C
Sine + No ise
Inv erte d Sawtooth
9 - Synthesizer Basics
Low Frequency Oscillators (LFOs)
G
Try combining the
E
Pattern LFOs, or
controlling the amount of
one with another, or
combining them with the
clock divisors.
147
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