1.12 LFOs

Using LFOs

  • An LFO is a low frequency oscillator
  • The frequencies used are below 20Hz, so they are inaudible
  • An LFO changes a parameter of an effect or processor according to another wave
  • Examples might be altering the delay time according to a sine wave. Other geometric waves can be used to change the effect of an LFO (e.g. square/triangle/pulse)

lfo1sine

Controls on Modulation Effects

  • Modulation effects have controls related to the rate and the depth of the modulation
  • Rate is how fast the periodic change of the parameter takes place (wave frequency)
  • Depth is how much the parameter is varied (wave amplitude)
  • The combination of both of these parameters can change whether the effect sounds subtle or very obvious

lfo2depth

Comb Filtering

lfo3comb

  • A comb filter adds a delayed version of a signal to itself, causing constructive and destructive interference.
  • The frequency response of a comb filter consists of a series of regularly spaced notches, giving the appearance of a comb.

 

Historical Production of Modulation Effects

 

Leslie Speaker

lfo4leslie

  • The Leslie speaker uses the Doppler Effect to create modulation, and is sometimes called ‘Rotary’ on effect plugins.
  • This is similar to the changing pitch heard when an ambulance passes you
  • It is a system of rotating speakers used primarily with the Hammond Organ in the 1960s
  • It occurs because the source of a sound changes position, relative to the listener.

The Eagles – Hotel California

The Beatles – Let It Be

Tape-Based Origins of Modulation Effects

  • Modulation effects were originally created by using two tape recorders

lfo6tape

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s