Oscillator
The Oscillator is the starting point of virtually all synthesis. Oscillators generate a fast, repeating signal that we hear as a waveform. It might be a smooth, undulating sine wave, a sharp sawtooth wave, or a boxy square wave, for example. Different oscillator modules offer different waveforms, and different controls for shaping the sound they produce.
In modular synthesis, most Oscillators need to be combined with other modules to create compelling sound. These extra modules will speak to the Oscillator via CV signals, allowing you to control the pitch and envelope of the notes produced.
More sophisticated Oscillator modules give you access to more niche and adventurous forms of synthesis, such as additive and FM synthesis. Depending on the kind of sounds you want to make, you could also explore other sound generators for your modular synth: for instance, a module that plays back samples, or a module that generates drum sounds.
Amplifier (VCA)
An Amplifier module is used to control the volume of other modules – typically Oscillators. In their basic state, most Oscillator modules in modular synthesis just output a continuous tone. You have to tell the module when to play a “note.” You can do this by sending it volume signals with an Amplifier module. This basic task makes Amplifier modules one of the simplest, and most essential, components in a modular rig.
Envelope Generator (EG)
An Envelope Generator can be used to change parameters over time – like the loudness of your synth sound – using editable shapes called envelopes.
Envelopes give contour to a sound. When you hear a synth bassline with a sharp attack that quickly fades away, or a pad that slowly arrives and lingers for a while, you’re hearing an envelope at work.
An Envelope Generator is likely to do at least two jobs in your modular rig.
Firstly, an EG patched to an Amplifier will allow you to shape the loudness of each synth “note” over time. Every time you want a note to play, you’ll need to trigger the Envelope Generator, which sends volume commands to the Amplifier, which in turn changes the volume of the oscillator signal.
That’s right: just to play “notes” with a modular synth, you’ll probably need at least three modules: an Oscillator, an Amplifier, and an Envelope Generator.
The other common job for an Envelope Generator is to control Filter Cutoff. But the flexibility of modular synthesis means you can get creative with how you use envelopes by hooking them up to other parameters. For instance, try patching your EG to the Oscillator’s pitch to make zippy lazer sounds.
The most common form of Envelope is ADSR. But there are many kinds of Envelope Generator module out there, offering funky envelope shapes and deep customization.
Other modulators
An Envelope Generator is a kind of modulator. That means it’s a module that doesn’t generate or process audio itself, but instead sends commands to other modules to make them behave in certain ways. Modulation is an essential part of all synthesizers. By making synth sounds move, modulation helps them to sound alive and unpredictable.
Your modular setup should have at least a few modulation modules. If you’ve used other kinds of synthesizer, you’ll be familiar with the other common modulator type: the Low Frequency Oscillator (LFO), which outputs a slow up-and-down signal, great for making your sounds drift and shimmer.
In most conventional synths, you can only assign your modulators to a few parameters. A modular synth lets you patch in your modulator anywhere that takes a modulating signal. This allows you to create complex routings and surprising sounds. You could even modulate your modulators, by using (for example) one LFO to change the depth or frequency of another LFO. This is when modular synths start to take on a life of their own.
Filter (VCF)
Filters shape the frequency content of a sound. They might do this by removing all the high frequencies above a certain point in the frequency spectrum (in the case of a low pass filter), or cutting unwanted low frequencies (high pass filter).
Filters play a crucial role in all synthesis, by shaping the raw sound that comes out of an oscillator to make it sound smoother and more controlled. Analog (or analog-modeled) EQs can also add character to the sound, particularly when you start turning up the resonance (steepness of the filter peak).
Most modular synth setups will need at least one filter. Preferably a low pass, though many manufactures offer “multi-mode” filters that can adopt different filter shapes for more versatility.
Try controlling a filter with an Envelope Generator to make your synth sound’s frequency profile change over time. But note: if you’re already using your Envelope Generator to control your Amplifier, you might need to get a second EG to control your Filter.
Trigger
One thing that sets a modular synthesizer apart is what it doesn’t have: a keyboard. You can add one if you like, by hooking up a MIDI keyboard to your rig using a MIDI to CV interface (which translates your MIDI notes into messages your rig can understand).
But there are other ways to tell your rig what to do. A Sequencer is a module that outputs a series of predetermined signals to create looping patterns. Sequencers can be used to program melodies, rhythmic patterns, and more – and are great for creating multi-layered music when you only have two hands. The most complex and exciting modular patches rely on clever use of Sequencers.