- Learn what additive synthesis is and how it works.
- Dive into the history and evolution of additive synthesis.
- Understand its strengths and limitations in music production.
Our ability to synthesize sound drastically changed the evolution of the music industry. During the ’60s and ’70s, the availability of commercially made synthesizers soared to new heights, and new-age sounds quickly became a staple tool in modern music.
However, it was well before the days of funky disco riffs and mind-altering analog bleeps that the first synthesizer was born. Additive synthesis became the first method in the history of sound synthesis.
In this article, we will look at what additive synthesis is, how it works, its history, and some of its strengths and limitations.
What is Additive Synthesis?
Additive synthesis uses the addition of sine waveform harmonics, or partials, to create complex waveforms.
A harmonic is any whole number multiple of a sound’s fundamental or lowest frequency. Blending these waveforms at varying frequencies, amplitude, and phase within their waveform cycle gives this type of synthesis its ability to produce a theoretically limitless array of sounds.
This synthesis method was conceptualized based on 19th-century physicist Joseph Fourier’s theory that all sound can be deconstructed into a series of interacting sine waves.
The sounds produced through additive synthesis vary greatly, from dissonant drones to atmospheric, evolving pads, chime, and bell-like sounds and synthesized vocal notes. In the hands of a master, the power of this synthesis style is immense.
Early additive synthesizers were not commercially available and were designed specifically for the study of sound, regardless of musical application. Throughout the decades, these machines allowed for the evolution of our understanding of how sound is made, thus providing the foundations for sound synthesis in music.
The Origins of Additive Synthesis
From as early as the third century BC, we can see evidence of the ideas for modern-day additive synthesis within the music world. Although not a true additive synthesizer, the pipe organ combines harmonic tones created by air blown manually through its pipes.
However, it wasn’t until 1862, following the development of Joseph Fourier’s theory of sound, that Herman von Helmholtz designed the Helmholtz Sound Synthesiser to study sound.
Again, this instrument was not technically a true additive synthesizer since the tones produced by an array of tuning forks were not pure oscillator-generated sine waves. However, it utilized the same concept of adding simple tones together to create harmonically rich sounds.
With the journey paved by many great minds, Thaddeus Cahill’s Telharmonium, invented in 1897, was the first true additive synthesizer. This colossal monster of a sound-making machine took up the ground space of an entire factory, with oscillators the size of grown men, and weighed in at around 14 tonnes. These massive electricity-powered oscillators were capable of producing pure sine waves.
A perhaps significant downfall of the earliest version of the Telharmonium was that it was inaudible. Invented before electronics and amplifiers, there was no way of hearing the sound signal being produced. Cahill solved this issue in 1902 with the help of the New York telephone service.
By pushing the phone receiver to its limits with an extremely high voltage, the Telharmonium’s signal was received and heard by gatherings of curious listeners. This dial-in music line was a subscription-based service, inspiring the first generation of electronic music fans.
Throughout the decades following Cahill’s invention, additive synthesis continued to evolve. The Hammond Organ, first manufactured in 1935, was the world’s first electromechanical organ and one of the first commercially manufactured portable synths. Though not using pure sine wave oscillators, its method of sound synthesis was additive.
The rise of digital technology made additive synthesis far more viable for commercial success. The Bell Lab’s ‘Alice’ was the first genuinely digital synth, built in 1977. During the ’70s and ’80s, additive synthesizers grew in popularity.
The Kawai K5, Synclavier II, Fairlight CMI, Wersi EX20, Qasar M8, and RMI Harmonic were among the many standout synths at the time. Popular software additive synths stating their place in today’s music scene include VirSyn’s Cube, Air’s Loom II, Native Instrument’s Reaktor, and Camel Audio’s Cameleon 5000.
Additive synthesis has appeared throughout the decades in a variety of successful music. Wendy Carlos famously used the Crumar GDS in 1982’s sci-fi hit film, Tron. Kraftwerk, Mark Fell, and Rian Treanor were among the creative minds that helped popularise additive synthesizers in modern music in the ’80s and ’90s. Thanks to producers like Kendrick Lamar and Ian Kirkpatrick, additive synthesis continues to be heard in popular music today.
How Does Additive Synthesis Work?
Although often complicated to use, additive synthesis itself is quite simple.
Multiple oscillators generate sine waves, the simplest sound wave we can produce. Each sine wave is a harmonic or partial variant of the fundamental frequency.
The fundamental frequency is the lowest frequency that we hear in a sound. Whereas a harmonic is a whole number multiple of that fundamental frequency.
An additive synth will have parameters that allow you to adjust a waveform’s amplitude, frequency, and phase. Although the theory of additive synthesis states that any sound can be produced, the synthesizer itself is limited by the number of oscillators (and parameters available for each oscillator).
To really understand how waveforms are manipulated using this method, let’s look at how sine waves interact. Here, we will look at three diagrams that show the simplest interactions between sine waves.
- When two sine waves at the same phase and frequency interact, the resulting waveform will be the average amplitude of the two initial sine waves. Diagram one shows constructive interference, where the resulting waveform is in the same phase as the two original waves, just with altered amplitude.
- However, when we add two sine waves together at opposite phases, we get something called destructive interference, as seen in diagram two. When two waveforms opposite in phase, with the same frequency and similar amplitude interact, these waves cancel one another out, resulting in little to no sound.
- Now that we understand the concept of constructive and destructive interference, let’s look at what happens when we adjust frequency, amplitude, and phase simultaneously. The resulting wave, seen in diagram three, is a hybrid of all combined sine wave characteristics.
Understanding the concept of wave interference is essential when using additive synthesis to achieve a desired sound. The more oscillators generating sine waves, the more we alter the frequency, amplitude, and phase of these waveforms, the possible outcomes become endless.
Resynthesis
Resynthesis is a concept used in advanced additive synthesis that allows for the reverse engineering of waveforms from a sample waveform. Essentially, the target waveform from a sample or recorded sound is mathematically analyzed and recreated using additive synthesis. This technology allows us to re-design and alter even the most complex of waveforms.
Pros & Cons Of Additive Synthesis
It is challenging to impartially categorize the advantages and disadvantages of various synthesis techniques since they are all unique methods for shaping audio. Nevertheless, it is feasible to identify some characteristic traits and limitations of additive synthesis.
| Pros Of Additive Synthesis | Cons Of Additive Synthesis |
| Highly complex waveforms | Expensive among analogs |
| Original synthesis approach | Fragile sound |
| AI improvements |
Why Use Additive Synthesis?
✔ Highly Complex Waveforms
Additive synthesis allows us to produce incredibly complex waveforms. In fact, any sound we can imagine can theoretically be produced using additive techniques.
✔ Original Synthesis Approach
For those who like the idea of old-school techniques and vintage sounds, additive synthesis is worth mastering. There’s a reason why there are so many die-hard fans of the early additive synths and their newer software cousins.
✔ AI Improvements
With the increasing use of artificial intelligence in modern software, it is seemingly inevitable that it will become a common tool in sound synthesis. Additive synthesis in particular can be incredibly tedious to learn, which turns away many users. However, AI could provide the solution to much of this difficulty, improving re-synthesis and allowing us to generate specific waveforms with ease.
Limitations of Additive Synthesis
Extremely Complex
Although its complexity is also why additive synthesis packs so much creative power, it makes it very difficult to use. With an element of guesswork and significant trial and error, producing specific sounds using this approach is not always straightforward. Hence, very few become true masters of additive synthesis.
Expensive Among Analogs
Because of their rarity and building complexity, analog additive synths are not the most affordable synthesizer option. Many of these hardware synths were produced in small batches due to the uncertainty of their commercial success.
However, during their release into the market, many producers hesitated to adopt additive synthesis, deeming it too challenging, and units were sold for a fraction of their original price.
Fragile Sound
Due to the nature of the additive synthesis approach, waveforms can interact negatively, causing waves to cancel one another out and create flat spots. A common complaint of additive synthesizers is their ‘thin’ sounds. This however can generally be avoided by understanding wave phasing.
Examples Of Additive Synthesizers
Classic Additive Synthesizers
Notable, classic additive synthesizers include:
- Kawai K5 (1987)
- Synclavier II (1980)
- Fairlight CMI (1979)
- Qasar M8 (1975)
Modern Additive Synthesizers
Modern additive synthesizers, including VST plugins, include:
- VirSyn Cube (2003)
- Native Instruments Reaktor (1996)
- Camel Audio Cameleon 5000 (2003)
- Air Loom II (2018)
Final Thoughts
As complicated and intimidating as it can be, additive synthesis allows for some incredible and theoretically limitless sound design opportunities. With the incorporation of artificial intelligence, additive synthesis has the potential to push the boundaries of sound-making like we’ve never seen before.
Before you go, why not brush up your skills with some related synthesis guides:
