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CHAPTER 5
Pro Edit
LFO (Low Frequency Oscillator)
Example B: “solo view” button active.
In addition to the main oscillator(s) of a synthesizer, which is responsible for the creation of
the audio signal itself, an LFO is an additional oscillator that operates at a comparatively
lower frequency (hence its name), that modulates the audio signal, thus causing a
difference to be heard in the signal without the actual introduction of another sound source.
Low Frequency Oscillation as a concept was first introduced in the modular synths of the
1960s and 70s — often its effect was ‚accidental‘; such were the extensive capabilities
of a modular synth operator to patch the instrument to create a vast array of different
configurations. They have since appeared in some form on almost every synthesizer,
and more recently other electronic instruments such as samplers have included them, to
augment their capacity for sound alteration.
The principle behind low frequency oscillation as a means of modulating a signal, as
opposed to adding to it, is that its frequency is lower than the audible frequency of the
human ear (20Hz–20kHz) i.e., the frequency is low enough so that it isn‘t heard as a tone.
A low frequency oscillator can be routed to control a variety of different parameters, for
example the frequency of the audio oscillator, the phase, panning, filter frequency, or the
velocity of the synthesizer’s output. For instance, when routed to pitch, an LFO serves to
simulate vibrato, and when an LFO modulates amplitude (volume), it creates tremolo.