Sound Synthesis Explained

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What is Sound Synthesis

Sound synthesis is about making or copying sounds with electronics, like synthesizers. These devices use electrical current (or 1s and 0s in the digital world) to play with sound waves to create audio signals.

This method lets us create a wide range of sound experiences that can’t be duplicated using acoustic instruments like guitars or pianos. However, in synthesis we can copy sounds from nature or create completely new sound patterns.

How Does Sound Synthesis Work

The core of the synthesis process involves the use of oscillators that produce various waveforms, each corresponding to a different pitch and quality of sound.

To oscillate means to move back and forth – i.e. we are creating a vibration that disturbs air particles, creating a wave that produces a sound that humans can hear.

We can then modify that wave to control how it sounds.

Things to Know

Looking into how sound synthesis works shows a mix of electronics, math and rules. These elements work together to make synthetic audio.

But you don’t need to be an engineer to start creating amazing sounds.

Here’s some stuff to know before going further:

  1. Hertz (Hz): Also known as “cycles per second” – a way to measure how fast a vibration is oscillating.
  2. Frequency Spectrum: Humans can hear vibrations that occur between 20 Hz and 20,000 Hz (or 20hz – 20khz)
  3. Oscillators: An electrical component or mathematical model that generates a waveform at specific frequencies.
  4. Amplitude: The maximum extent of a vibration or oscillation. Basically the “strength” of an audio signal, or “height” of an audio wave
  5. Resonance: When a signal/wave vibrates at its maximum amplitude (strength) due to a specific frequency, called the “resonant frequency.”
  6. Resonant Frequency: The natural frequency at which an object (like a string) vibrates, impacting the perception of the sound it generates.
  7. Harmonics: Components of a sound wave that resonate at different frequencies, shaping the tonal quality of sounds (color, character, timbre, etc.)
  8. Overtones: Higher frequency components of a sound wave that contribute to its unique tonal quality, produced when it vibrates in multiple modes simultaneously
  9. Envelopes: Adjustable parameters that control the changes in a sound’s amplitude (i.e. volume/strength) over time
  10. Filters: A mechanism for filtering out (i.e. removing) certain frequencies from an audio signal.
  11. Modulation: A technique of changing or adjusting the waveform/signal to achieve a specific sound in terms of strength/tone/pitch/etc.
  12. Effects Processing: Using various “effects” (ex/ reverb, echo, distortion, etc.) on an audio signal to achieve a desired sound.
  13. Velocity Sensitivity: Controlling the amplitude and other characteristics of a sound based on how hard a note is hit/struck.

Understanding these foundational concepts is vital for anyone interested in the art of synthesizing sounds. They can be difficult to wrap your head around at first, so read through all that slowly, a few times.

If you still don’t understand a concept fully after this guide, use Google or ChatGPT to help you.

Synths in Front of a Nebula

Sound Synthesis Example

Sound synthesis is a world full of many techniques (described in more detail below), each with its own special way of making and changing audio signals to produce musical sounds.

Analog synthesizers make sounds using electrical signals, while digital ones use mathematical formulas. And most recently, AI algorithms are being used to generate sounds as well.

Let’s say you want to emulate a piano sound through analog or digital audio synthesis (learn the difference between the two). What would you do?

Creating a piano sound with a synthesizer would involve several steps:

  1. Waveform Selection: Choose a basic waveform (or multiple) that is close to the piano sound. This will serve as the foundation for your piano sound.
  2. Envelope Shaping: Adjust the amplitude envelope to mimic how a piano sound starts, sustains and fades.
  3. Harmonics and Overtones: Add some harmonics and overtones to add depth and richness to the sound. This can be done by layering sounds at different pitches or using a filter to boost certain frequencies.
  4. Effects Processing: Add a reverb effect to give the sound some space and to emulate the acoustic properties of a piano in a room.
  5. Fine Tuning: Fine-tune your settings until you achieve the desired piano sound. This may involve adjusting the parameters mentioned above or adding additional effects.

There are many creative ways to implement the above workflow using various forms of synthesis technology – both hardware and software based.

For example, additive synthesis stacks up sine waves, whereas subtractive synths remove harmonics, and FM synthesizers change waves in complex ways.

How to Synthesize Sounds

Different ways of creating sounds, like subtractive, additive, FM, and wavetable, each have their own unique controls and sound options.

By exploring these methods, we can understand the many different sounds that can be created for music or other types of audio production.

But before we dive into that, let’s talk a bit about your tools.

How Synthesizer Parts Works

Hardware synthesizers generate sound through analog circuitry, with oscillators creating raw waveforms that are shaped by filters and modulated by low-frequency oscillators (LFOs) and envelopes.

In contrast, software synthesis (learn more) relies on digital signal processing and math models to simulate these analog processes, offering a broader range of possibilities due to the computational power of modern computers.

Understanding the functional principles of oscillators, filters, envelopes, and LFOs is essential to grasping the how of sound synthesis and design.

How Oscillators Work

Oscillators are key parts in hardware and software synthesizers. They create the first sound frequencies that form the sound’s nature in the synthesized audio.

An oscillator makes a signal by boosting and shaping electronic noise when electrical current passes through it. It does this by creating a steady wave (a repeating signal that fluctuates) at a certain frequency. This is done over and over again.

This signal can take the shape of various waves, like sine, square, triangle, or sawtooth.

Here are the basic steps:

  1. The oscillator starts with an electrical voltage signal. This signal fluctuates up and down in a particular waveform.
  2. The rate at which the signal fluctuates (its frequency) determines the pitch (i.e. the musical “note”) of the sound. Faster fluctuations result in higher pitched sounds (higher notes), while slower ones result in lower pitched sounds (lower notes).
  3. When this electrical signal is sent to a speaker or headphone, it causes the speaker cone to move back and forth.
  4. This movement pushes and pulls on (i.e. vibrates) the air around it, creating pressure waves that travel through the air.
  5. When these pressure waves reach our ears, our eardrums vibrate and our brains interpret these vibrations as sound.

How Filters on Synthesizers Work

Filters are key tools in making a synthesizer’s unique sound. They help musicians change the way sound waves from oscillators are heard.

A filter is basically an equalizer that removes frequencies above or below a certain point.

Methods like low-pass (reducing/removing HIGH frequencies) and high-pass (reducing/removing LOW frequencies) help shape sound by changing the strength of certain frequencies that we end up hearing.

Other types of filtering include:

  1. Band-Pass: allowing a certain “band” of frequencies (frequencies within a specific range) to pass through while reducing/removing frequencies outside this range.
  2. Notch: reduce/remove frequencies within a certain range while allowing frequencies outside this range to pass through.

In all these cases, the filter works by altering the amplitude (strength/height of wave) or phase (how different sound waves interact in time/space) of certain frequencies, which can change the overall sound of the audio signal.

Using these filters, musicians can have fun with “resonance effects.”

These can range from loud, sharp sounds at high resonance to softer, bouncy sounds at low resonance. This helps create unique sound changes.

High Pass Filter Screenshot
A high pass filter set at 100 Hz

How Envelopes on Synthesizers Work

Envelopes help improve a synthesizer’s output by carefully managing how each note played changes over time. They allow for exact control of how a sound plays, letting musicians shape the tone and modulation of the sound.

These changes are vital for shaping the sound’s tone. Most often they’re referred to as ADSR envelopes – Attack, Decay, Sustain and Release. However you may also see different types of envelopes like AHD (Attack, Hold, Decay) and others.

An ADSR envelope affects:

  • Attack: how quickly a sound starts and hit’s it’s maximum amplitude when a note is pressed
  • Decay: how quickly the sound fades to it’s “sustain” level of amplitude,
  • Sustain: how long the decayed sound lasts while the note is held down
  • Release: how long it takes the note to end or fade

Think of the differences in ADSR between a sharp hand clap and a large, ringing bell tower. Each sound will start, fade, hold and end in a different way.

By shaping this “envelope” you can start to create and mimic various types of sounds.

ADSR Envelope Diagram

How an LFO Works

A Low-Frequency Oscillator, also known as an LFO, is an important tool that adds variety and motion to a sound generated by another oscillator. But it doesn’t make any sound itself.

LFOs help create cool sound effects like vibrato or tremolo by “oscillating” back and forth at a low speed. They can modulate (i.e change/alter) the frequency of a soundwave or the filter on a soundwave, among many other things.

These modulations can be set at a constant rate or can be synced with the tempo of a song for a more natural sound.

Sound Synthesis Techniques and Types Explained

Synthesis in audio includes many techniques, each with a special way to create and change audio.

From the basic ideas of Analog Synthesis to the complex sound changes of FM Synthesis, these techniques offer a wide range of choices for those who design sounds and make music.

Here’s a brief breakdown of each type/technique.

How Analog Synthesis Works

Analog synthesis is a key part of making electronic music. It uses oscillators, filters, and modulators to shape basic waveforms into complex sounds.

Artists use voltage control to alter signal processing with patch cables. This lets them modify frequency and create harmonics. They make sounds by putting oscillators into filters. This process, called subtractive synthesis, shapes sound textures. This gives analog synthesis its warm, unique quality.

How Analog Modeling Synthesis Works

Virtual-Analogue Synthesis is a method that uses computer calculations to copy the complex details of analog sound creation. It’s like capturing the unique aspects and minor flaws in classic analog circuits in a digital form.

This method uses “component modeling” to accurately reflect the responses of real-life analog parts.

It’s never quite “perfect,” but damn have we come close in recent years. The level of this imitation relies on the processing power of the computer hardware used. It can’t go beyond its limits.

But also the complexity of how analog circuitry affects a waveform is very difficult to imitate precisely,

How FM Synthesis Works

Frequency modulation (FM) synthesis (read more) is a powerful tool for sound designers. It uses the interaction of oscillators to create a range of complex sounds.

There are two waveforms – the “carrier” (original waveform) and the “modulator” which alters the carrier’s frequency content. This process changes the sound of the resulting waveform over time, creating rich and varied sounds.

A ‘modulator waveform’ can take many forms, but a sine wave is often used because it’s simpler to control its effects. When the carrier and modulator interact, they create new frequencies, known as sidebands. These sidebands aren’t found in either the carrier or modulator waveforms.

FM8 Screenshot
FM8 – A Virtual FM Synthesizer

How Granular Synthesis Works

Granular synthesis (read more) is a method that splits up audio into tiny parts called grains.

These grains are then changed and put back together to create new sound textures. This method is great for things like stretching out time and shifting pitch.

By changing key settings—like grain size, position, and spray—artists can discover unique soundscapes. This helps enhance their work with rich, textured audio.

How Additive Synthesis Works

Additive synthesis (read more) lets you build complex sounds by stacking individual sound waves together. Each wave adds to the overall sound color and quality.

You can use this method to copy natural sounds or create unique electronic sounds.

It’s all about tweaking the harmonics. This can make the sound very clear. But, it can be tough to handle many sound waves at once. This is why some people prefer simpler ways to make sounds.

How Subtractive Synthesis Works

Additive synthesis makes sounds by stacking sine waves. But, subtractive synthesis (read more) does it differently. It begins with complex waveforms and removes certain frequencies to create the wanted sound.

This process uses oscillator changes to make basic waveforms. It also uses filter changes to take out certain harmonics. There’s also envelope shaping to change sound over time, and LFO changes to add life and movement to a sound.

These methods of shaping sound give us the warm, classic sounds we associate with analog synthesis.

How Modular Synthesis Works

Modular synthesis is a method that lets us make complex sounds using several different pieces of gear.

It works by connecting separate, individual parts – oscillators, filters, effects, etc. – or ‘modules.’ This way of making sounds is very flexible and encourages creativity.

Modules are linked by using 3.5mm mono cables to connect them in countless ways. This process is controlled by changing the voltage passing through each module, which adjusts the sound wave.

A Modular synthesizer Setup
A large modular synthesizer setup

How Wavetable Synthesis Works

Wavetable synthesis (read more) is a method of creating sound by playing back pre-recorded audio samples or a set of waveforms, called “wavetables.” You can move through or change this wavetable to make different sounds.

These wavetables are often short, looped recordings of complex waveforms.

The pitch of the sound can be manipulated by changing the playback speed of the wavetable. Additionally, the timbre or tone of the sound can be altered by crossfading or interpolating between different wavetables.

How West Coast Synthesis Works

Don Buchla first introduced West Coast synthesis (read more) in the 1960s. It’s known for encouraging users to try new things and create unusual sounds. It contrasts with the East Coast synthesis by focusing more on experimentation and the manipulation of waveforms.

The process often includes the use of complex oscillators, wave shapers, low pass gates, and function generators.

Sound is typically created and modified through a method called “wave shaping,” which manipulates an oscillator’s output to create complex harmonics. This method makes use of random voltages to tweak/modulate various parameters of the sound leading to unpredictable variations in sound.

For making these complex compositions, it uses new sequencing methods and things like frequency shifting to make unique sound textures.

How Sample Based Synthesis Works

Sample-based synthesis (read more) is a method of creating sound by using pre-recorded audio files, known as samples. These samples can be any sound, such as musical instruments, vocals, or sound effects.

Once digitized, the sound can be manipulated in a variety of ways. It can be looped, pitched, reversed, time-stretched, or processed with effects to create something enhanced or entirely new/different. It can also be layered with synthesized sounds and modulated like any other audio signal.

The manipulated sample can then be played back like an instrument.

This allows for unique and complex sounds that would be difficult or impossible to generate with traditional synthesis alone.

How Microchip Synthesis Works

Microchip sound synthesis (read more) is a technique of generating sounds from actual sound chips used in old computing hardware.

Also known as chiptune or chip music, it is prevalent in a musical style that emulates the simplistic electronic “beep-boop” sounds of vintage computers, video game consoles, and arcade machines.

The technique involves programming these sound chips to produce desired notes and rhythms, creating a unique genre of electronic music. This form of music production started back in the 1980s and was commonly heard in early video games, computer programs, and even some popular music.

Today, many artists and musicians still explore and celebrate this nostalgic form of sound synthesis, either by using original old hardware or modern emulation software.

The appeal of microchip sound synthesis lies in the unique tonal quality of the sounds and the technical challenge in creating complex and intricate music from such a rudimentary source.

How Vector Synthesis Works

Vector synthesis (read more) is a method of creating sounds by mixing and crossfading between multiple waveforms or sound sources.

It uses a two or four point controller (often displayed as a joystick or XY pad) to determine the blend of these sources. This controller can often be automated over time, creating complex and evolving sounds.

The term was popularized by the Sequential Circuits Prophet VS synthesizer which used this method.

Vector synthesis allows for a wide variety of tones and timbres to be created, making it a versatile tool in sound design.

Different Uses of Sound Synthesis

Sound synthesis is used in many areas, from music making to sound design in movies and video games. It gives a wide range of sound textures and tones that are key to the creative process.

The change from analog to digital tools has changed how artists and engineers work with sound. Digital synthesis lets creators copy real-world sounds or make new sound experiences.

In music, sound synthesis is very important for electronic styles. Here, synthesizers are the main part of the music. Artists use different synthesis methods to make unique sounds that show their musical style.

Apart from music, synthesizers are used to make sound effects in films. This gives the audience a deep sound experience. From the quiet sound of a spaceship to the loud roar of a magical beast, synthesized sounds add to the story by improving what you see on screen.

Video games also use a lot of sound synthesis to make lively audio settings. Game sound designers use synthesis to make sound effects and to react to what the player does.

This makes the experience interactive and fun. Sound synthesis helps to build virtual worlds, making them feel real and interesting for the player.

In education and research, sound synthesis is used to study sound phenomena and psychoacoustics. This helps scientists understand how we hear and interpret sounds. It’s also used to make auditory interfaces and assistive technologies.

Here, synthesized sounds give information or help users who can’t see well.

What to Do Next

Thanks for reading this complete guide on audio synthesis for beginners. Next up, choose an area you’d like to start learning with from the list below and read our guide on how to get started.

  • Learn the Difference Between Analog and Digital Synthesis In-Depth – Read Now
  • Learn Different Types of Synthesis In-Depth – Read Now
  • Learn About How Various Types of Synthesizers Work – Read Now
  • Learn How to Make Your Own Synthesizer VST
  • Learn How to Build Your Own Hardware Synth