Additive synthesis: An introduction to theory, practice and history

Additive synthesis is one of the basic methods of sound synthesis used in music production and sound design. It makes it possible to create sounds by adding harmonic partial tones and is widely used in both the software and hardware world of electronic music production. This blog post provides a comprehensive introduction to additive synthesis, the story behind it, typical settings, and shows various software and hardware options that use this technique.

What is Additive Synthesis?

Additive synthesis is based on the theory that each sound can be represented as a combination of sine waves superimposed with different frequencies, amplitudes and phases. Each of these sine waves is called ‘partial’ or partial tones, and the basic idea of additive synthesis is to create sounds by summing (adding) these partial tones. In contrast to subtractive synthesis, in which a harmoniously rich sound is formed by filtering, additive synthesis often begins with nothing and builds up complex sounds by the gradual addition of partial tones.

The History of Additive Synthesis

Additive synthesis has a long and fascinating history dating back to the early days of electronic music. One of the first and most significant milestones in the history of additive synthesis was the invention of the telharmonium in the late 19th century by Thaddeus Cahill. This instrument used huge rotating waveforms and electric amplifiers to create tones through additive synthesis. Although the Telharmonium did not have a sustainable commercial future, it laid the foundation for the development of modern synthesizers.

Another important step in the history of additive synthesis was the development of the Hammond organ in the 1930s. This organ used an electromechanical method to create tones created by additive synthesis. The Hammond organ quickly became a popular instrument in jazz, gospel and rock music, and its unique sound possibilities are still sought after today.

In the 1970s and 1980s, additive synthesis experienced a renaissance when digital technologies such as the Yamaha DX7, one of the first popular digital synthesizers, came onto the market. Although the DX7 primarily used frequency modulation (FM), the underlying principles of additive synthesis were part of its sound design. Later, in the 1980s, additive synthesis was integrated into software environments such as Csound and Music V, creating new possibilities for sound design.

Modern hardware and software for additive synthesis

Today, additive synthesis is widely used in both the hardware and software worlds. There are many modern synthesizers and software plug-ins that use this technique to create complex and unique sounds.

Modern and available hardware for additive synthesis

1. ASM Hydrasynth (2020):
   • description: The ASM Hydrasynth is a hybrid digital synthesizer that combines additive synthesis with wavetable synthesis. It features a polyphonic aftertouch keyboard, a user-friendly macro controller and a flexible modulation matrix. The Hydrasynth allows the user to create and modulate up to 8 harmonic overtones, providing rich and complex sound textures.
   • Special characteristics: Wavetable oscillators, extensive modulation capabilities, built-in effects and MPE (MIDI Polyphonic Expression) support.
2. Modal Electronics Argon8 (2019):
   • description: The Modal Argon8 is a wavetable synthesizer that also offers additive synthesis. With 32 oscillators (8 per voice) and a variety of sound modulation options, the Argon8 can harmoniously produce rich and dynamic sounds. It is known for its high-resolution oscillator wavetables and spectral manipulation capabilities.
   • Special characteristics: 32 high-resolution oscillators, various filter modes, sequenceable arpeggiators and customizable effects.
3. Korg Modwave (2021):
   • description: The Korg Modwave is a powerful wavetable synthesizer that integrates additive synthesis in the form of wavefolding and spectral modulation. This combination makes it possible to create complex textures and vivid sounds that can be further adapted through comprehensive modulation options.
   • Special characteristics: Extensive wavetable library, Motion Sequencing 2.0, Kaoss Physics and multi-level effects.
4. Roland Jupiter-X (2019):
   • description: The Roland Jupiter-X is a polyphonic synthesizer that integrates additive synthesis along with other forms of synthesis (such as virtual analog, FM, and PCM). It offers the opportunity to recreate classic Roland sounds and create new, complex sounds through additive methods.
   • Special characteristics: Multiple oscillator and filter types, model expansion technology and extensive effects.

Modern and available software for additive synthesis

1. UVI Falcon 2 (2019):
   • description: UVI Falcon 2 is a state-of-the-art hybrid software workstation that supports multiple types of synthesis, including additive synthesis. With a huge collection of oscillators, effects and modulation tools, users can create an unlimited number of sounds. The additive engine allows detailed editing of up to 256 partials.
   • Special characteristics: Comprehensive oscillator types, advanced modulation capabilities, scriptability, and a large library of presets and extensions.
2. Arturia Pigments 4 (2023):
   • description: Arturia Pigments 4 is a versatile software synthesizer that offers additive synthesis alongside subtractive, wavetable, FM and granular synthesis. With a user-friendly interface and powerful modulation system, Pigments 4 allows you to create unique animated sounds through additive methods.
   • Special characteristics: Additive harmony section, numerous modulation sources, poly-aftertouch support and over 1200 presets.
3. Sugar Bytes Aparillo (2018):
   • description: Aparillo is an experimental FM and additive synthesizer that specializes in creating soundscapes and cinematic sounds. The additive component allows control over harmonic content and the spectral management of sounds.
   • Special characteristics: Unique orbit modulator, FM synthesis combined with additive control and deep sound shaping capabilities.
4. Reason Studios Parsec 2 (2020):
   • description: Parsec 2 by Reason Studios is an advanced spectral synthesizer that uses additive synthesis. It offers detailed control over spectral shaping and an intuitive user interface that allows manipulation of up to 512 harmonic partial tones.
   • Special characteristics: Two additive engines, spectral filters and dynamic modulation.
5. Kiloheart's Phase Plant (2019):
   • description: Phase Plant is a modular synthesizer that integrates an additive engine. Users can add modules as needed, creating complex additive setups that can be combined with wavetable, subtractive, and FM synthesis.
   • Special characteristics: Modular design, extensive effect chain, flexible modulation matrix and many add-ons for further sound design.

How to use Additive Synthesis?

Additive synthesis requires a basic understanding of sound and how it can be manipulated. Unlike other forms of synthesis, which often target immediate, broad changes (such as cutting off frequencies in subtractive synthesis), additive synthesis requires a more detailed approach. Here are some basic steps and settings to use additive synthesis in practice:

1. Setting basic partial tones

In additive synthesis, you usually start with a fundamental tone, also known as the first partial tone or fundamental frequency. Depending on the desired timbre, additional partial tones (overtones) can be added. Each of these overtones has its own frequency, amplitude and phase.

• frequency: Determines the pitch of the part.
• Amplitude: Determines the volume of the part.
• Phase: Influences the temporal course of the part.

2. Apply envelopes

An envelope defines how the sound develops over time. The most common envelope types are ADSR (Attack, Decay, Sustain, Release). Each partial tone can have its own envelope, which means that the sound can be changed in a very complex way over time.

3. Using spectral modulation

Some additive synthesizers, such as Razor and Harmor, offer the ability to modify the entire frequency spectrum. These modulations can drastically change harmonic content and are great for creating interesting textures and movements in the sound.

4. Insert filters and effects

Although filters are not the main tool in additive synthesis, they can still play a role. Filters can be used to remove unwanted frequencies or amplify certain frequencies. In addition, effects such as reverb, delay and distortion can be used to add depth and character to the additive sounds.

Typical attitudes and techniques

Here are some typical settings and techniques you can use in additive synthesis:

1. Harmonious chords: By creating sounds that contain multiple basic tones and harmonic overtones, you can create rich, chord-like sounds. This is useful for creating pads and atmospheric sounds.
2. Detuning and Spread: The slight tuning of partial tones and the distribution of these partial tones in the stereo field can create a wide, chorus-like effect that is ideal for leads and pads.
3. Spectral animation: By modulating partial tones in real time, you can create sounds that change subtly or drastically over time. This can be controlled by LFOs or envelopes and is especially useful for dynamic soundscapes and basslines.

conclusion

Additive synthesis is a powerful technique of sound synthesis that makes it possible to produce sounds in a very detailed and controlled way. Its history goes back over a century, and its application in modern music productions shows that it continues to be a valuable tool for musicians and sound designers. With a variety of hardware and software options and the flexibility to produce virtually any conceivable sound, additive synthesis remains a fascinating and versatile field worth exploring further.

Whether you're an experienced sound designer looking to explore the limits of sound manipulation, or a newcomer looking for a new way to create creative sounds, additive synthesis offers a profound and exciting world of sound design just waiting to be discovered.

📚 Further literature on Amazon (affiliate links)

🎛️ Foundations & Practice of Additive Synthesis

• Virtual Sound: Sound Synthesis and Signal Processing – Theory and Practice with Csound
  This book provides a comprehensive introduction to sound synthesis with Csound, including practical exercises on additive synthesis.
• Creating Sounds from Scratch: A Practical Guide to Music Synthesis for Producers and Composers
  A practice-oriented guide to sound design that covers various synthesis techniques, including additive synthesis.

📘 Other relevant titles

• The Computer Music Tutorial
  Curtis Roads offers a comprehensive reference work on computer music, which also covers additive synthesis in detail.

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