From One Note to an Orchestra — How a Synthesiser Actually Creates a Sound
Every enormous synthesiser sound begins with something surprisingly simple.
Listen to the soundtrack of a modern film, a piece of electronic music, a television theme or even some contemporary organ arrangements and you may hear enormous sounds: deep basses that seem to shake the room, sweeping strings, powerful brass, shimmering pads and strange effects that appear to come from another planet.
It is easy to imagine that these sounds must start life as something equally complicated.
Usually they do not.
A synthesiser can begin with one of the simplest sounds imaginable: a single electronic waveform.
From that very modest beginning we can progressively change its harmonic content, its volume, the way it starts and finishes, its movement through time and finally the acoustic space in which we imagine it being played.
That is synthesis.
And one of the things I particularly enjoy about programs such as VCV Rack 2 is that they make this process remarkably visible. Instead of simply selecting a preset called "Epic Cinematic Strings", we can actually build the sound and see the virtual cables connecting one stage to another.
So let us start with almost nothing.
Stage One: One Oscillator and One Note
At the heart of many synthesiser sounds is an oscillator.
An oscillator produces a repeating electrical waveform. When that signal is converted into audio, we hear a musical note.
If the oscillator produces 440 cycles every second, for example, we hear the note A above middle C.
Written simply:
Frequency = 440 Hz
Double the frequency:
Frequency = 880 Hz
and we hear an A one octave higher.
Halve it:
Frequency = 220 Hz
and we hear an A one octave lower.
Already we have one of the fundamental relationships between physics and music.
But frequency only tells us the pitch. It does not tell us what the sound is like.
For that we need to look at the shape of the waveform.
Start with the Simplest Sound: The Sine Wave
A sine wave is perhaps the simplest possible oscillator waveform.
It contains essentially one fundamental frequency and no strong additional harmonics.
Play one through a loudspeaker and it can sound almost unnaturally pure.
It does not sound very much like a violin.
It certainly does not sound like a trumpet.
And it probably will not make anyone think they have just heard a magnificent cinema orchestra.
But it is an excellent place to begin because there is very little in the sound to start with.
In VCV Rack 2 our first virtual patch could therefore be extremely simple:
Oscillator -> Audio Output
Connect a keyboard or use a virtual control to change the oscillator frequency and we already have a playable electronic instrument.
Admittedly, not a terribly exciting one.
But we have created sound.
Different Waveforms, Different Ingredients
Change the oscillator waveform and things immediately become more interesting.
Common synthesiser waveforms include:
Sine
Triangle
Sawtooth
Square
Pulse
A sawtooth wave contains many harmonics and consequently sounds much brighter and richer than a sine wave.
A square wave contains a different pattern of harmonics and can produce the characteristic hollow or woody sound associated with many electronic instruments.
A triangle wave sits somewhere nearer the sine wave in character, but with additional harmonic content.
This gives us our first important lesson in synthesis:
The oscillator provides the raw material.
It is rather like choosing the material from which we are going to make something. We might start with wood, steel, clay or plastic. What we eventually construct depends partly upon the material with which we started.
The same is true of sound.
But Real Instruments Do Not Simply Switch On
There is another problem.
If we connect an oscillator directly to the output, the sound simply exists continuously.
Real instruments behave differently.
Strike a piano key and the sound begins sharply before gradually fading.
Blow a trumpet and the sound takes a fraction of a second to establish itself.
Bow a violin gently and the sound can swell gradually.
Hit a drum and the sound appears almost instantly and then rapidly disappears.
The way that a sound changes through time is enormously important to how we recognise it.
This brings us to one of the most useful parts of a synthesiser.
The Envelope: Giving the Sound a Beginning, Middle and End
Most synthesisers use some form of envelope generator to control how a sound changes over time.
A very common envelope is ADSR:
Attack - Decay - Sustain - Release
Attack
How quickly does the sound rise from silence to maximum level?
A percussion sound might have an extremely short attack.
A slow string pad might take a second or two to swell into existence.
Decay
After reaching its initial peak, how quickly does the sound fall towards its sustained level?
Sustain
How loud does the sound remain while the key is held?
Release
What happens after the key is released?
Does the sound stop almost immediately, or does it gradually fade away?
Already we can make our simple oscillator behave much more like an instrument.
Our patch is becoming:
Oscillator -> Amplifier -> Audio Output
with an envelope controlling the amplifier.
In modular synthesiser language the amplifier is often called a VCA, or Voltage Controlled Amplifier.
Now pressing a key can make the sound appear and releasing the key can make it disappear naturally.
That alone makes an astonishing difference.
The Filter: Sculpting the Sound
Our sawtooth oscillator may contain plenty of harmonics, but perhaps it is too bright.
This is where a filter becomes useful.
One of the most common is the low-pass filter.
A low-pass filter allows lower frequencies through while progressively reducing frequencies above a selected cutoff point.
Imagine our oscillator producing a bright, buzzy sound.
Set the filter cutoff high and much of that brightness remains.
Gradually lower the cutoff and the sound becomes warmer and darker.
Lower it still further and eventually very little remains.
Our signal path might now become:
Oscillator -> Filter -> Amplifier -> Output
and our envelope still controls the amplifier.
Suddenly we have the foundations of an extremely useful synthesiser.
But we can do more.
Let the Envelope Control the Filter Too
Instead of leaving the filter in one position, we can make its cutoff frequency change every time we play a note.
This is where synthesis becomes particularly interesting.
Suppose a note begins very bright and then rapidly becomes darker.
We can use another envelope to make the filter open quickly when the note begins and then gradually close.
That relatively simple change can transform a static electronic buzz into something that feels much more alive.
The patch might conceptually become:
Oscillator -> Filter -> VCA -> Output
with:
Envelope 1 -> VCA
and:
Envelope 2 -> Filter cutoff
Now different parts of the sound are changing independently over time.
We are beginning to design rather than merely generate sound.
Building a Simple Synth Bass
Let us turn this into something practical.
Start with a sawtooth oscillator.
Step 1 — Oscillator
Choose a sawtooth waveform and play it fairly low.
On its own it will probably sound rather harsh.
Step 2 — Filter
Pass it through a low-pass filter and reduce the cutoff.
The aggressive high frequencies disappear and the sound becomes thicker and warmer.
Step 3 — Amplifier envelope
Give it:
Fast attack
Short decay
Moderate sustain
Short release
Now each note feels firm and controlled.
Step 4 — Filter envelope
Make the filter open rapidly as the note begins, then close slightly.
Instead of a dull "booo", we obtain more of a:
BWAAH
That changing harmonic content is a large part of what gives a synthesised bass its character.
Step 5 — Add a second oscillator
Add another oscillator an octave lower or slightly detune two oscillators against one another.
The bass becomes much bigger.
We have moved a considerable distance from our original sine wave.
And we still have not added any effects.
Turning the Same Idea into Strings
Now let us change the design.
Strings generally need a much gentler beginning.
We might use two or three sawtooth oscillators, detuned very slightly so they are not perfectly identical.
Instead of an immediate attack, give the amplitude envelope a slower attack.
Perhaps:
Attack: moderate
Decay: gentle
Sustain: high
Release: fairly long
Immediately the notes begin to swell rather than simply switching on.
Filter some of the harsh high-frequency content away.
Then introduce a little chorus to create the impression of several slightly different sound sources.
Finally add reverb.
We are now moving towards a broad string pad.
The fascinating thing is that the basic components have hardly changed.
We still have oscillators, filters, envelopes and amplifiers.
We have simply changed how they behave.
What About Brass?
Synthetic brass provides another good example of just how important envelopes can be.
A sawtooth waveform is again a useful starting point because real brass instruments contain plenty of harmonic information.
But the filter behaviour matters enormously.
A brass-like sound often benefits from the filter opening strongly at the beginning of the note before settling slightly.
Add a relatively fast amplitude attack, a strong filter envelope and perhaps two slightly detuned oscillators.
Suddenly the same collection of modules that produced our string pad starts producing something much more forceful.
It will not necessarily fool anyone into believing that a real French horn section has materialised in the room.
That is not really the point.
The important lesson is that we are learning which characteristics make us perceive a sound as being brass-like.
That understanding becomes extremely useful when arranging music.
And Then We Can Abandon Reality Completely
A synthesiser does not have to imitate anything.
This is where things become particularly entertaining.
We can create a science-fiction sound precisely because there is no physical instrument against which it needs to be judged.
Take an oscillator.
Add another oscillator.
Allow one oscillator to change the frequency of the other.
Add a slowly moving filter.
Introduce an LFO — a Low Frequency Oscillator — to make some part of the sound rise and fall automatically.
Add delay.
Add a very large reverb.
Perhaps add distortion.
Suddenly we have something that might accompany:
A spacecraft passing overhead
A mysterious alien transmission
A futuristic computer
A game interface
A cinematic transition
A piece of experimental music
At this point there is no "correct" sound.
The question becomes:
Does the sound create the feeling we want?
That is just as important in music production as knowing what note comes next.
What Is an LFO?
An LFO is another oscillator, but usually one running too slowly for us to hear it directly as a musical note.
Instead, we use it to control something else.
For example:
LFO -> Pitch
can produce vibrato.
LFO -> Amplifier
can create tremolo.
LFO -> Filter
can make the tone repeatedly become brighter and darker.
This is one reason modular synthesis becomes so fascinating.
Almost anything can control almost anything else.
The output from one module becomes the instruction for another.
And this is exactly what VCV Rack 2 allows us to see.
Why VCV Rack 2 Is Such a Useful Teaching Tool
Traditional hardware modular synthesisers are wonderful things, but building a substantial collection can become expensive rather quickly.
VCV Rack provides the same basic modular idea on the computer screen.
You can place an oscillator on the virtual rack.
Add a filter.
Add an envelope generator.
Add an amplifier.
Then connect them with virtual patch cables.
That makes the signal path much easier to understand.
Instead of a synthesiser appearing to be a mysterious box containing hundreds of knobs, we can follow the process:
Generate -> Shape -> Control -> Modify -> Output
Once that principle makes sense, much larger synthesisers become far less intimidating.
The Complete Beginner Patch
A very useful first VCV Rack experiment would therefore be:
Keyboard/MIDI -> Oscillator
Oscillator -> Low-pass Filter
Filter -> VCA
VCA -> Reverb
Reverb -> Audio Output
Then add:
Keyboard Gate -> ADSR Envelope
ADSR Envelope -> VCA control
That is enough to create a proper playable synthesiser voice.
Once it works, change one thing at a time.
Change the oscillator waveform.
Listen.
Change the filter cutoff.
Listen again.
Increase the attack.
Listen again.
Increase the release.
Add more reverb.
Listen again.
This approach is much more useful than randomly turning twenty knobs simultaneously because it allows us to hear what each control actually contributes.
The Reverb Makes a Bigger Difference Than You Might Expect
There is something almost magical about the moment reverb is added to a dry synthesiser sound.
Our basic patch might sound as though it is coming directly out of a small electronic box.
Add a little reverb and suddenly the brain begins imagining a physical space.
Increase it further and the instrument might appear to be in a concert hall.
Push it much further and it might sound as though it is being played inside an enormous cavern.
For cinematic music, ambient sound and science-fiction effects, this can completely change the emotional character of the sound.
But effects should usually enhance a sound rather than rescue a poor one.
If possible, create an interesting sound first.
Then decide where it should appear to exist.
Delay, Chorus and Distortion
Once we have the basic voice working, effects provide another level of sound design.
Chorus
Chorus creates the impression of several slightly different versions of the same sound playing together.
It can be particularly useful for strings and pads.
Delay
Delay repeats the sound after a short period.
One note can become:
Note... note... note... note...
Different delay times and feedback settings can produce everything from a subtle thickening effect to enormous rhythmic patterns.
Distortion
Distortion introduces additional harmonics and can make a sound aggressive, powerful or deliberately rough.
Used gently it can add character.
Used heavily it can completely transform the source.
Again, the important question is not simply, "What does this control do?"
It is:
What emotion does this change create?
Sound Design Is Really a Collection of Small Decisions
One of the misconceptions about synthesis is that experienced sound designers somehow know exactly how to produce a complicated sound instantly.
In practice, much of sound design is experimentation.
Start with something simple.
Change something.
Listen.
Decide whether it is moving in the right direction.
Change something else.
Listen again.
You might discover something better than the sound you originally intended to create.
That is part of the attraction.
This Also Changes How You Listen to Music
Once you begin creating sounds, you start listening differently.
Instead of hearing "a synthesiser", you may find yourself asking:
Is that a sawtooth oscillator?
Is the filter slowly opening?
Is there a long attack on the envelope?
Are several oscillators detuned?
Is that chorus or simply multiple layers?
How much of that enormous sound is actually reverb?
Is there a low-frequency oscillator creating the movement?
This is rather like learning about photographic lighting.
Once you understand key light, fill light, backlight, colour temperature and direction, you start noticing them when watching films.
Understanding how something is constructed changes the way you experience the finished result.
From Synthesis to Film and Video
This becomes especially useful when creating music for video.
Suppose a film begins with an aerial view of a landscape.
A slowly evolving pad may fit beautifully.
A technology demonstration might benefit from a clean rhythmic electronic sound.
A dramatic product reveal could use a deep synthesised bass swell.
A science-fiction sequence might use sounds that have no equivalent in the real world.
The synthesiser is therefore not simply an electronic musical instrument.
It becomes a sound-design tool.
And because the sound is being built rather than simply selected, it can be shaped specifically around the images.
A Preset Is Useful — Understanding It Is Better
Modern software synthesisers come with thousands of excellent presets.
There is absolutely nothing wrong with using them.
I use presets too.
They are extremely useful starting points.
But understanding synthesis changes how we use them.
Instead of thinking:
"That preset is nearly right, but I need to find another one."
we can think:
"That preset is nearly right. Perhaps I need a slower attack, slightly less filter cutoff and a little more release."
That is a very different relationship with the instrument.
We stop simply choosing sounds.
We start shaping them.
The Connection with the Organ Is Closer Than It First Appears
There is also an interesting parallel with organ playing.
An organist combines stops to create a particular tone.
Different ranks contribute different harmonic characteristics.
Registration determines whether the instrument sounds delicate, bright, powerful, orchestral or theatrical.
A synthesiser approaches the same overall challenge differently, but the underlying question is remarkably similar:
What combination of sounds produces the character I want?
Whether working with a church organ, theatre organ, modern arranger organ or modular synthesiser, understanding how sounds combine is just as important as knowing which notes to play.
You Do Not Need to Be a Musician to Experiment
Perhaps the best thing about synthesis is that you do not need years of musical training before you can explore it.
You can begin with one oscillator.
Connect it to a filter.
Move the filter control.
Listen to what happens.
Add an envelope.
Change the attack.
Listen again.
Add reverb.
You have now started sound design.
Music theory certainly becomes useful when we want to create melodies, harmonies and arrangements, but synthesis itself can be explored as a mixture of music, physics, electronics, computing and experimentation.
That combination is one of the reasons I find it so interesting.
From One Note to an Orchestra
So how does a synthesiser produce an enormous sound?
Usually not by doing one enormous thing.
It does lots of small things.
An oscillator creates the basic waveform.
Another oscillator may reinforce it.
A filter removes or emphasises parts of the harmonic spectrum.
An envelope determines how the sound changes through time.
An LFO introduces movement.
A VCA controls its level.
Chorus makes it wider.
Delay creates repetition.
Reverb gives it space.
Then several different synthesised sounds can be layered together.
And suddenly that tiny electronic waveform with which we began has become something that can fill a soundtrack.
That is the real fascination of synthesis.
Behind some of the biggest sounds in modern music lies a remarkably simple idea:
Create a sound. Shape it. Make it move. Put it into a space. Then listen.
And if it is not quite right?
Move a virtual cable, turn a control and try again.
That experimentation is not a failure to understand the synthesiser.
It is exactly what synthesis is about.
Philip M Russell Ltd
Photography • Video • Music • Creative Production • Education
#MusicProduction #SoundDesign #Synthesiser #Synthesis #VCVRack #VCVRack2 #ModularSynth #ElectronicMusic #MusicTechnology #MusicEducation #FilmMusic #AudioProduction #MusicTheory #CreativeTechnology #PhilipMRussellLtd
