History: What is a low frequency oscillator?

What is a low frequency oscillator?

• A low frequency oscillator changes a parameter over time.
  That is the purpose of an LFO, not the definition.
• A low frequency oscillator is an oscillator with a frequency below the human range of hearing.
  Excellent!
• A low frequency oscillator is the effect of modulating the amplitude of a sound source.
  That is tremolo.
• A low frequency oscillator is the technique of varying parameters to sound generators and sound modifiers over time.
  No, that is modulation.