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Synthesizer Basics – Lesson 3

Synthesizer Basics 3

Lesson 1 went over the common components of a synthesizer, explained the functions of the Oscillators, and the mixer sections. Lesson 2 looked at the Envelope and filter sections of the synth. This time we’ll get into using the LFO and arpeggiator sections and polyphony options.


LFO stands for Low Frequency Oscillator. This oscillator typically functions in the 0 to 20Hz range, but this oscillator isn’t a tone generator but actually a control voltage to modulate the other parts of the synth.
There are just three basic controls for the LFO section
⁃    Rate (or speed)
⁃    Waveshape
⁃    Depth

Rate sets how many cycles per second the LFO operates at.
The Waveshape sets how it behaves. The waveshape options will be the same as in the tone generating Oscillators
Depth sets how much effect the LFO will have on the functions it’s assigned to
Often you’ll find the depth controls are on each of the other functions, like the Oscillators, and filter. In this case its very likely that the knob will be labeled LFO and pointing straight up is off. Turning the knob to the left or right will cycle that function down and up, or up and down.
Other synths will just have a single depth knob and some way to assign the LFO to just one parameter.
Enough talking about what it does, let’s here what it can do.
In this example there will be a tone with no LFO, then -50% modulation for oscillator 1, then 50% for the filter with a triangle waveshape.


That’s a bit extreme but used more lightly you can add a nice movement to your patches.


An arpeggiator is a built-in sequencer for the synth. When you play note or chord it will play each note sequentially. Not all synths will have an arpeggiator.
An arpeggiator has three main controls
⁃    Pattern
⁃    Rate
⁃    Gate

The pattern control chooses how the sequence will be played. Upward, downward, and random are common but you’ll usually have several variations.
Rate is the speed the sequence is played back at. In a virtual synth you can lock it to the project tempo and choose something like 16th notes.
The gate control can shorten the length of each note independent of the release in the amplifier section.
Here is a simple C-Major chord going through the arpeggiator. First set to 1/4 notes, then 8th notes, then I’ll change the pattern from Upward to downward, then I’ll shorten the notes with the gate.



Many synths will have options to control the polyphony or how many notes can be played at once. Some synths are monophonic and can only play one note at a time. Other synths allow you to choose from one to hundreds of voices. The MiniMoog was monophonic and remains one of the greatest and most imitated synthesizers. It’s amazing what you can do with one note at a time.


With monophonic synthesizers you can use the portamento function to quickly (or slowly) bend up or down in pitch to the next note without re-triggering the envelope.

Here is an example of that in action:


That’s it for part 3. We covered the LFO, Arpeggiator, Polyphony and Portamento. Start digging into these functions and try them out.
Have fun!


  1. Äleyo
    Äleyo January 9, 2017

    Lesson 4 would be great !

  2. roy ciporin
    roy ciporin June 12, 2019

    Lesson 4 would indeed be great. so far I loved your work

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