In the context of electronic music, an LFO (Low Frequency Oscillator) and a VCO (Voltage-Controlled Oscillator) are both commonly used to modulate sound waves through frequency modulation (FM) or amplitude modulation (AM). However, there are key differences between the two components.
LFO (Low Frequency Oscillator): An LFO is an oscillator that generates waveforms at frequencies below the audible range (typically below 20 Hz). It is primarily used for modulating other parameters, such as pitch, filter cutoff, or amplitude, rather than generating audible tones directly. LFOs produce slow, cyclical waveforms such as sine, triangle, square, or sawtooth waves. The LFO's output is typically routed to control the rate or depth of modulation for other components.
VCO (Voltage-Controlled Oscillator): A VCO is an oscillator that generates audible frequencies within the range of human hearing. It produces waveforms at various frequencies determined by the control voltage applied to it. VCOs are the fundamental sound generators in analog and modular synthesizers. They often offer a wide range of waveforms, including sine, triangle, square, sawtooth, and more complex waveshapes. The pitch of the VCO can be controlled by a keyboard, sequencer, or other voltage sources.
When it comes to modulation:
Frequency Modulation (FM): FM involves changing the frequency of a waveform using another waveform as a modulation source. In this context, both LFOs and VCOs can act as modulation sources. An LFO can modulate the frequency of a VCO, resulting in a shifting pitch effect, while a VCO can modulate the frequency of another VCO, creating more complex timbral changes.
Amplitude Modulation (AM): AM involves modulating the amplitude (volume) of a waveform using another waveform. While both LFOs and VCOs can be used as modulation sources for AM, it is more common to use an LFO for amplitude modulation. The LFO's cyclical waveform, such as a triangle or square wave, is often used to create rhythmic or pulsating effects by controlling the amplitude of the sound.
In summary, the main difference between an LFO and a VCO lies in their frequency ranges and primary functions. LFOs generate low-frequency waveforms for modulating other parameters, while VCOs produce audible tones and are typically used as the primary sound source. However, both can be used for frequency modulation (FM) and amplitude modulation (AM) to shape and modulate sound in electronic music.