The Fundamentals of Serum Synthesizer

The Fundamentals of Serum Synthesizer

Welcome to Sonicallys complete beginners introduction to Serum Synthesizer. Below we will go over the meanings of the many parts of serum, and hopefully by the end of this blog it wont look so scary! Lets do this!

The Oscillator

The heart of a synthesizer! The oscillator produces a raw, unfiltered sound wave. In an analog synthesizer, an oscillator will generate a saw wave, square wave, sine wave, triangle wave, or noise. In digital synthesizers, like serum, the core of the oscillator can be a wavetable or even a recorded sample. 

The Five Basic Waveforms Explained

In synthesisers you will come into contact with the following five basic waveforms:

  1. Sine
  2. Triangle
  3. Square/Pulse
  4. Saw
  5. Noise

A sine wave is a very clean sound, it has no harmonics, just a single fundamental – think of a heart rate monitor going “beep, beep, beep”.

Sine wave in serum synthesiser Sonicallys

A triangle wave has a similar sound to a sine wave but it does have some added harmonics – think of a flute.

Triangle wave harmonics serum synthesiser sonicallys


A square wave is packed with harmonics and has a sound reminiscent of 8-bit video games.

A saw wave is rich in harmonics and has quite a rough and harsh sound to it – some words that come to mind are – gritty and buzzing.
saw wave serum synthesiser harmonics sonicallys
Noise is completely random frequencies spread across the entire spectrum and sounds like a TV or Radio that hasn’t been tuned. Noise is extremely useful for sound designers and can be used to make anything from Claps, to Sweeps, to Hi-Hats, to adding top-end to synths and loads more.
noise in serum synthesiser sonicallys


The ADSR Envelope Explained

ADSR envelope example serum sonicallys

ADSR is for Attack, Decay, Sustain, and Release. 

We use the ADSR envelope to control the amplitude of our waveform over time. When we push a key on our synthesizer the very first stage that gets triggered is the Attack.

The Attack stage will control the amount of time the sound takes to reach its peak volume level when a key is pressed.

However when you press a key on a pad sound it might take 2 seconds for the sound to reach its maximum loudness. In this case, the Attack would be set to 2 seconds. Think for example the violinist, bowing their instrument, and as there bow moves across the string, their pressure on the string increases, and the sound grows to a peak, this would be a real world example of a long attack.

Here is an example of an envelope with a short attack

Here is an example of an envelope with a long attack
envelope with a long attack time serum sonicallys


The next stage that gets triggered when we press a key is the Decay.

Decay will begin immediately once the attack stage is complete. Decay is the amount of time it takes the sound to decrease in volume to the level of the Sustain.

Here is an example of an envelope with a short decay

envelope with short decay example serum sonicallys


Here is an example of an envelope with a long decay

envelope with long decay example serum sonicallys


Sustain is the level that the sound will remain at while we are holding the key down and the decay stage is finished.

Here is an example of an envelope with a maximum sustain

envelope with sustain example serum sonicallys


Here is an example of a sound with a low sustain

envelope with low sustain example serum sonicallys


Release is the amount of time it takes for the sound to decrease in volume until it is silent. This stage only triggers once we release the key.

Here is an example of a sound with a short release

envelope with short release example serum sonicallys
Here is an example of a sound with a long release
envelope with long release example serum sonicallys


The best description I have heard about filters is that they are like the tongue and lips of your synth. We can move them up, down and around to shape our sounds, to make them appear up front and loud or to push them back in the mix.

In the context of a synthesizer, a filter is a module that removes certain frequencies from the audio signal, much like an equalizer on a stereo or a recording console. 

Low Pass Filter – Removes all frequencies that are above the cutoff point. Most commonly used for plucks, pads, leads and basses.

Low Pass Filter for Serum Synthesizer Sonicallys


High Pass Filter – Removes all frequencies below the cutoff point. Most commonly used for growls.

High Pass Filter for Serum Synthesizer Sonicallys


Band Pass – Removes frequencies that are above and below the cutoff. Great for sweep effects and in some cases leads.

Band Pass Filter for Serum Synthesizer


Notch – Scoops out frequencies at the cutoff point. Good for creating distorted bass sounds.

Notch Filter for Serum Synthesizer


There are a ton of different filters available in Serum, but these are the basic 4 which you will most regularly use.


Simply put, think of modulation as using one thing to control the movement of another. 

Modulation analogy in serum synthesiser Sonicallys


With modulation, we typically use the ADSR envelope or an LFO (explained below) and map it to another parameter like volume, pitch or filter cutoff, causing the control to alter slightly as the sound progresses but within the limits defined by the envelope.


LFO Stands for Low-Frequency Oscillator. It’s just an Oscillator that is played back a lot slower than usual and then gets used to modulate other parameters like pitch, volume, filter cutoff etc.

The easiest way to think of an LFO is to think of an ADSR envelope that is not restricted by stages. Remember an ADSR will progress through the envelope as you do certain things (hit the keys, time elapses, then release the keys etc). However as soon as a key gets pressed the entire shape of the LFO cycles through on repeat until you release the key.

LFOs are typically good for creating rhythms, or things that require repetitive motion like vibrato, or making a dubstep growl that is constantly changing. Learn more about music theory with our free PDF.

Monophony & Polyphony

Most synths will give you an option to choose between mono and poly.

Dont Stress! This simply dictates how many notes can be played at the same time.

Mono, meaning one, and poly, meaning multiple. So if you are creating a lead and don’t want notes to overlap, mono will work. However, if you are creating a patch that will be playing chords you will need a polyphonic synth.

Unison & Detune

Unison is the number of "voices" an oscillator will put out.

If you have any wave and set the unison to 2 – when you press a key down the synth will output 2 waves, both at the exact same pitch.

These waves are called voices.

If you played a chord with 3 notes and 2 voices of unison the synth would output a total of 6 waves, 2 for each key that is pressed. (If you're interested in learning more about chords check out our blog post)

Increasing unison will cause the synth to output multiple waves at the same pitch. However there is another parameter called “detune” that will shift the pitch of each voice slightly so that they are all out of tune with each other.

The more you increase the detune, the more the timbre of the synth becomes dissonant. (learn all about this with our free music theory pdf here)

Serum is set up to be wide by default but will play everything back in mono until you increase unison and detune, or add effects to it.