Important Synthesis Modules and Audio Production

For music producers understanding synthesis and its modules helps us to hear and understand timbre and sound. In synthesis we create sounds from scratch which helps us to hear how where the sound comes from and how it evolves via the different modules.

Also, as music producers the chances are great that we will be working with synthesizers and samplers which now play important roles in many forms of music. There has been a recent reemergence of modular synthesizers such as the famous Moog which has been around at the early days. The modules used in these historic models are still the basis of many modern versions – both hardware and software.

Fundamentals of Synthesis

The fundamentals of synthesis are related to five modules and the way they are connected. These modules are the building blocks that most synthesizers are built upon. These modules are the oscillator, filter, amplifier, LFO and envelope.

Oscillator (VCO)

The oscillator creates the sound. This sound is based on a geometric wave form such as a sine, saw tooth, square, triangle or noise. This sound can be very raw and bright. The oscillator is also known as a voltage control oscillator (VCO).

The oscillator’s sound can change over time (modulate). This can be the pitch/frequency – controlled by a keyboard going from key to key. The key controls how the sound changes over time.

The sound changes based on the wave that is used. Square is hollow (because it’s missing the even partials) and sounds like an instrument like a clarinet. The saw tooth can be bright and sustaining (with all upper partials) and can emulate a string instrument such as a violin or cello.

Filter (VCF)

The sound travels from the oscillator to the filter. The filter is also known as the Voltage Controlled Filter (VCF). The job of the filter is to remove the unwanted frequencies with the low pass filter playing an important role. It allows the lows to get through while eliminating a proportion of the highs. This helps smooth out the bright oscillator sound making it more real worldly. Often the filter is considered the most important part of the synthesizer. The classic Moog synthesizer is renowned for the great sound of its filter.

Filters can be changed from low pass to high pass or band pass, band stop or notch. The filter can be modulated – often via the filter cut off – which dulls the sound.

Resonance (feedback) is an important facet of the filter. If you turn up the resonance it emphasizes the cutoff frequency.

Amplifier (VCA)

After the oscillator and filter the sound reaches the amplifier which controls the volume of the sound and how it develops over time (modulation). It is also known as a voltage controlled amplifier (VCA).

The VCA is an amplifier whose gain is set by the voltage level of a control signal. Mostly they attenuate the sound rather than amplify it. The VCA determines the instantaneous volume level of a played note, and it quiets the output at the end of the note.


The envelope creates a shape that runs every time a key is pressed. It is mostly controlling the main amplifier – this is how we can make the amplitude change over time. The result is percussive shape or a sustaining shape. Envelopes can also control pitch, filters and other parameters.

The envelope performs a specific shape every time a key is pressed. The sound path goes up, down, sustains and disappears. The path takes the form of ADSR which stand for attack time, decay time, sustain level, and release time.

In a synthesizer the attack actually dulls the beginning of the note. The more you increase the attack – the slower it will develop. Attack takes it up to 100% and then the sound decays down to the sustain level which is a steady state. Once it’s released it goes down to zero.   Very much like holing a key down and releasing.

Low Frequency Oscillator (LFO)

The LFO is a modulator which creates cyclic variations in any other parameter. Often it is controlling the pitch of the oscillator as a vibrato. This tends to give the sound a warmer, richer sound much like the vibrato of a string instrument. LFOs can also control filters, amplifiers, other LFOs and other parameters.

We usually cannot hear the LFO as it is used as a control signal for changing parameters of synthesizers or effects. An LFO is a low frequency oscillator. An LFO usually runs below 20 Hertz. The vibrato of a singer or string instrument is in the three to six Hertz range.

There can be many more of these individual modules in a complex synthesizer and they can connect in large variety of ways. The LFO also uses wave shapes such as square, saw tooth and sine.

Synthesis Modules and Audio Production

We have looked at the usage of the 5 most important synthesis modules: the Oscillator, Filter, Amplifier, Envelope, and LFO and how they relates to audio production. We have observed how these help us understand timbre and sound – and also the importance of synthesizers in modern day music.