LFO's

Introduction

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

The LFOs has some basic parameters:

Delay : This parameter sets how much time takes since the start of the note to the start of the LFO
When the LFO starts, it has a certain position called Start Phase
Frequency: how fast the LFO is (i.e. how fast the parameter's controlled by the LFO changes)
Depth : the amplitude of the LFO (i.e. how much the parameter's controlled by the LFO changes)

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

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 folowing images are shown some examples of randomness and how changes the shape of a triangle LFO.
LFO Randomness Examples

Other parameters are:

Continous mode - If this mode is used, the LFO will not start from "zero" on each new note, but it will be continuous. This is very usefull if you apply on filters to make interesting sweeps.
Stretch - It controlls 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:
LFO settings in ZynAddSubFX

Theese 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 Randomnes
F.R. - LFO Frequency Randomness
C. - LFO Continous Mode
Str. - LFO Stretch - in the image above the LFO stretch is set to zero