LFO: Low Frequency Oscillator
Definition: An oscillator used as a modulation source, usually below 20hz.
(Creative Recording 1 Effects and Processors - Paul White 1999 )
The LFO used within modulation creates repeating variations in a sound such as vibrato and tremolo. As mentioned in the definition, the waves are usually around the lower level of human hearing which means that the wavelengths are very long. This creates a warm, rotary motion when combined with other oscillations.
There are many different ways in which the connections of the modules previously mentioned can be connected. The diagram below illustrates the most common connections.
Note that the direction of the audio signal only travels in one direction. The modules connected via the vertical lines (control signals) do not affect the signal directly and the sound would still start and finish in the same place without them.