If you are taking the Intro to Music Production course through coursera.org, please skip to the next paragraph. If you are not, here is a quick debriefing on what this blog post is all about : ) I enrolled in the aforementioned production course online (it’s free, by the way, so you might want to check it out for yourself) and part of the evaluation process involves us having to re-teach an element of the coursework. Since this information might be useful to other people, I thought I’d post these assignments on my blog. That being said, I am a student (not an expert), so don’t take what I say here as the ultimate truth. In fact, if you have other insights that might enhance or correct my understanding of the content, I’d love for you to leave a comment at the bottom of the post : )

What is a Synthesis Module?

According to The Synthesizer Academy, modules of a synthesizer are “the logical sections that each do their part to generate or modify a signal”.  Depending on the brand and type of synth you are using, these modules may all be included in the same piece of hardware (or its digital equivalent) or you might have to patch them together if they are physically separate from each other (or digitally presented in this way). Below are the five most important synthesis modules and their common uses.

Oscillator (VCO)

The Voltage Controlled Oscillator is the “sound creator” in modular synthesis and is used to generate sound through geometric wave forms such as: Sine, Triangle, Sawtooth, Square, Pulse, and Noise waves. Depending on the complexity of your synth, you may be able to access multiple wave forms at the same time or (with simpler synths) you might be restricted to a single wave.

Though synthesized sounds don’t typically sound like natural instruments, wave shapes are related to how sound is created in the ‘real world’. For example, square waves (above) are missing all the even partials of the harmonic spectrum, making their shape switch-like (up/down or on/off) and their sound hollow – like a clarinet whose wooden reed vibrates rapidly, opening and closing the passage way for air to travel down the hollow, cylindrical body.

Unlike non-synthesizing oscillators, the pitch of these sounds can be modulated (changed) over time through devices (such as MIDI controllers and other synthesis modules) that are connected to the oscillator’s Control Voltage (CV) input.

In short, the oscillator module in synthesis can be used to create sound and modulate pitch.

Learn more about VCOs and their controls here.

Filter (VCF)

After sound leaves the oscillator, it typically enters the Voltage Controlled Filter- considered by some to be the most important part of a synth, because it is the module most responsible for shaping tone/spectrum of sound and giving a synth its unique character. While simple synthesizers will have one filter (usually low pass) available to you, complex synths will have many.

Like the oscillator, filters can also be modulated. The most common (and perhaps important) way to modulate sound through a filter is with the frequency cut off (often controlled by key position, envelopes, or an LFO). For example, this type of modulating can be used to create a sweeping sound that goes from dull to bright over time.

Because geometric waveforms are typically very bright, Low Pass Filters tend to be a common choice. This filter reduces the high end (including harmonics) by allowing frequencies below the frequency cut off to pass through, while blocking any frequencies above that cut off. Other types of filters may be desired, however, when trying to emulate specific sounds.

Unlike the EQ section of a mixing board, where pristine sound is typically desired (settings are configured subtly so that the audience hears the authentic sound, not the effect ON the sound), filters in synths are resonant (boosting) and frequency cutoff boosts can be a very creative tool in sound production. For example, a phaser-like effect can be created by modulating the frequency cutoff level while resonance is high. However, if you only want to reduce or remove unwanted frequencies, using resonance would be counterproductive.

In short, the filter module can be used to create boosts, dramatic sweeps, and control the tone or character of synthesized sounds. Different filter types are good for emulating different types of sound.

Learn more about VCFs and their controls here.

Amplifier (VCA) & Envelope

Usually the last module in the chain, the Voltage Controlled Amplifier controls how much of a signal is allowed to pass through over time. This is accomplished with instructions from an Envelope Generator (EG). Envelope shapes tell the synth how the amplitude controls should respond over time once a signal is sent (by hitting a key on your MIDI keyboard, for example). This is different from an envelope in a compressor, which creates a path as it follows the signal; Synth envelopes create the path before the signal is sent by manipulating ADSR (Attack time, Decay time, Sustain Level, and Release time).

Attack Time – is how long it takes the amplitude of a sound to go from 0% to 100% when the signal is triggered/key is pressed. Thus, the longer the attack time, the longer it takes to get to 100% and the duller the sound will be.

Decay Time – is how long the signal takes to reduce itself to the designated sustain level.

Sustain Level – is how long the note will stay at a steady state until the trigger/key is released.

Release Time – is how long it takes for the signal to go from the sustain level to 0% after the trigger/key is released.

In short, Voltage Controlled Amplifiers and Envelopes are used to control the change in amplitude when a signal is triggered to go through the synth (such as when you press a key on a MIDI controller or keyboard), making sounds more or less percussive or sustained in nature, and can create “swell” effects.

Learn more about VCAs and their controls here and the ADSR envelope here.

Low Frequency Oscillator (LFO)

Low Frequency Oscillation is a rhythmic pulse below the threshold of human hearing (20 Hz) that is used to control other modules/parameters within the synthesizer. Its cyclic and wavering nature makes it ideal for emulating vibrato. You can do this by setting the LFO (source of modulation) to 3-6 Hz with the VCO as your destination of modulation.

In short, LFOs are used to modulate cyclic variations in other modules (wavering pitch, volume, and timbre – for example).

Learn more about LFOs and their controls here.