1. LFO 101 – understanding modulation basics
1
In addition to audible oscillators, most synths feature at least one Low Frequency Oscillator (LFO). As the name implies, an LFO is an oscillator that operates far more slowly – usually below the range of human hearing (sub 20Hz). It usually can’t be heard in itself in the signal path – it’s used to influence other synth parameters instead.
2
Let’s modulate the pitch of Dune CM’s first audible oscillator using one of the synth’s three identical LFOs. As with many synths, this is set up via a modulation matrix – In the cental panel, we’ll open the Mod Matrix 1 > 12 tab, then set the Source to LFO1 and Destination to Osc 1 Semi. The more you drag up the centre
Amount value, the more you’ll hear LFO 1 increasingly wobble Osc 1’s pitch.
3
The ‘shape’ of this pitch-wobbling is a smooth, up-and-down curve, because LFO 1’s shape is set to a Sine wave. Click the four toggle buttons on LFO 1’s left to change between four shapes: Downwards Saw, a downwards sloping ‘zap’; Square, a strict ‘on-off’ shape; a smoothly-curved Sine; and Sample-and-Hold, an unpredictable, random shape. Try them out and hear how they each affect the pitch movement.
4
The LFO’s Rate (sometimes called
Speed or Frequency in other synths) is its speed, measured in cycles per second, or Hertz. Increase or decrease this value to speed up or slow down the modulation. Most LFOs allow you to lock the speed to your DAW’s tempo – punch Sync to do that in Dune CM. Now, when you change the Rate amount, the speed is set in rhythmic divisions of a bar – 1/2, 1/4, 1/8 etc.
5
Although we said that LFOs operate below the range of human hearing (ie, below 20Hz), this isn’t always the case. Many LFOs, as with Dune CM’s, can actually be sped up to super-fast rates
above 20Hz, which is known as audio-rate modulation. Detoggle Sync, then increase
Rate to hear the generation of metallic, gnarly sideband harmonics.
6
Toggle the Reset button, and the LFO modulation will restart with every new MIDI note. Fade-In allows you to delay the LFO’s onset, so it kicks it gradually as a note as played. Skew essentially bends the wave shape. Check out Dune CM’s Quick Guide PDF in the CM Plugins folder for more details.