LFO
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:author: Paul Nasca

Introduction
~~~~~~~~~~~~

"LFO" means Low Frequency Oscillator.
These oscillators are not used to make sounds by themselves, but they change
some parameters (like the frequencies, the amplitudes or the filters).

The LFOs have some basic parameters:

* *Delay*: This parameter sets how much time it takes since the start of the
           note to the start of the LFO.
* *Start Phase*: The position that a LFO will start at . 
* *Frequency*: How fast the LFO is (i.e. how fast the parameter is controlled by
               the LFO changes)
* *Depth*: The amplitude of the LFO (i.e. how much the parameter is controlled
           by the LFO changes)

image:images/lfo0.png[]

Another important LFO parameter is the shape.
There are many LFO Types according to the shape.
ZynAddSubFX supports the following LFO shapes:

image:images/lfo1.png[]

Another parameter is the LFO Randomness.
It modifies the LFO amplitude or the LFO frequency at random.
In ZynAddSubFX you can choose how much the LFO frequency or LFO amplitude
changes by this parameter.
In the following images, there are shown some examples of randomness and how it changes
the shape of a triangle LFO.

image:images/lfo2.png[]

Other parameters are:

* *Continuous mode*: If this mode is used, then the  LFO will not start from "zero" on each new note, but it will be continuous. This is very useful if you apply on filters to make interesting sweeps.
* *Stretch*: It controls how much the LFO frequency changes according to the
note's frequency.
It can vary from negative stretch (the LFO frequency is decreased on higher
notes) to zero (the LFO frequency will be the same on all notes) to positive
stretch (the LFO frequency will be increased on higher notes).

User Interface
~~~~~~~~~~~~~~

In ZynAddSubFX, LFO parameters are shown as:

image:images/uilfo.jpg[]

These parameters are:

* *Freq*: LFO Frequency
* *Depth*: LFO Depth
* *Start*: LFO Start Phase - 
If this knob is at the lowest value, the LFO Start Phase will be random.
* *Delay*: LFO Delay
* *A.R.*: LFO Amplitude Randomness
* *F.R.*: LFO Frequency Randomness
* *C.*: LFO Continuous Mode
* *Str.*: LFO Stretch - in the image above the LFO stretch is set to zero
