Modulation

When one type of oscillator is used to affect another, this is called modulation. Modulation can be applied to filters or even the waveform before it is sent to output, depending on the synthesizer.

The Low Frequency Oscillator
One of the examples of modulation include the application of the low frequency oscillator. This is just an oscillation; we don't use it as a sound, but we use its back-and-forth nature as an algorithm for wiggling the settings in our synthesizers as the music plays.