Additive vs. Subtractive Synthesis: What's the Difference

Additive vs. Subtractive Synthesis: What's the Difference Additive vs. Subtractive Synthesis: What's the Difference

Among the myriad ways to craft sounds using synthesis, additive and subtractive synthesis are two of the four main pillars alongside FM and wavetable synthesis.

Understanding the basics of each method can help you lay a foundation for a deeper connection with your music and your synthesizers (both software and hardware), allowing you to articulate precisely what you hear in your mind's ear.

In this guide, we're going additive and subtractive synthesis in-depth, so you can start using these techniques to shape your sounds and open new doors to creative expression.

What Is Additive Synthesis?

I like to think of additive synthesis like painting with a blank canvas. To get the sound you want, you have to meticulously add one stroke at a time. In this case, these strokes are harmonics. This method operates on the principle that any complex sound can be broken down into its fundamental components, which are pure sine waves at various frequencies, amplitudes, and phases.

Additive synthesis works by constructing sound from the ground up, which provides a pretty high degree of control and precision.

Of course, you might be thinking,

What in the world are harmonics?

In their simplest definition, harmonics are essentially the multiple frequencies that make up a sound. Each harmonic is a pure tone or a sine wave, that contributes to the overall timbre and character of the sound. The first harmonic, or the fundamental frequency, determines the pitch we perceive, while the subsequent harmonics (overtones) add texture, richness, and color.

In additive synthesis, harmonics are the small components we can sculpt and manipulate to create unique sounds.

The process begins with silence. From there, we can selectively add harmonics and adjust their frequencies, amplitudes, and phases to create the desired sound. The one downside to the meticulous nature of additive synthesis, however, is that it can be both CPU-intensive and demanding in terms of our understanding of sound structure.

A History of Additive Synthesis

The history of additive synthesis can be traced back to one of humanity's oldest and most majestic musical instruments: the church pipe organ . This grand instrument embodied the principles of additive synthesis long before the term was coined, as it combined different pipes, each of which produced a single tone, to create a fuller, more complex sound.

By pulling various stops, organists could effectively layer these tones, controlling the mix of harmonics in real-time, a process remarkably similar to modern additive synthesis.

This concept of constructing sounds from individual components was revolutionized and made more accessible with the advent of the Hammond Organ in the 1930s. The Hammond differed from the traditional pipe organ in several ways, most notably how it generated sound. Instead of relying on air passing through pipes, it used tonewheels to create its oscillations, which produced a richer, somewhat more complex tone. The Hammond also introduced drawbars, so players could manipulate its sound in a manner reminiscent of what additive synthesis would become, albeit with a fixed set of harmonic choices rather than the infinite possibilities.

The leap to true additive synthesis in electronic instruments was marked by the introduction of the Kawai K5 in the late 1980s. The K5 was one of the first digital synths to use additive synthesis as its core sound generation method. Unlike its predecessors, the K5 allowed users to manipulate individual harmonics directly, offering an unprecedented level of control.

With this synth, you could sculpt sounds by adjusting the amplitude, frequency, and phase of up to 128 harmonics in real-time, which paved the way for the intricate and detailed sound design that defines software-style additive synthesis today.

Additive Synthesis in the Digital Era

Additive synthesis has undergone a serious transformation in the digital ear, much of which has been propelled by pure computing power. Today, you can find endless software synthesizers that harness the power and possibilities of additive synthesis. Here are a few of my favorites:

Logic Pro - Alchemy

Once a standalone synthesizer, Apple eventually integrated Alchemy into Apple Logic Pro. This synth features a robust additive engine with a blend of sampling and synthesis. It's particularly strong for morphing between sounds.

Beyond its spectral and additive synthesis capabilities, you'll find a massive library of sources and effects, making it a versatile tool for creating lush pads and dynamic leads.

Image-Line - Harmor

Harmor takes a comprehensive approach to sound design, exactly like what you'd expect from Image-Line. It takes additive synthesis to the next level by integrating image synthesis, where you can literally transform pictures into sound, offering a unique bridge between visual and auditory media.

The re-synthesis capabilities also allow you to manipulate existing sounds at a harmonic level, making it a powerful tool for both creating new sounds and transforming sampled audio.

Native Instruments - Razor

Razor is one of my favorite additive synthesizers out there. It has carved out a niche in the digital synth market with its cutting-edge, ultra-modern design. Made with today's producer in mind, it delivers sharp, rich, and immensely detailed sounds.

The interface is gorgeous a well, and it provides tons of visual feedback that makes the intricate process of shaping harmonics bot intuitive and engaging. In fact, one of Razor's main features that I love is its ability to manipulate sound in a visually immersive environment. Plus, with a dynamic range of filters, effects, and modulators, you can craft everything from aggressive, Hans Zimmer-style basses to floaty, ethereal pads. It might be one of the most versatile synths on the market today.

What Is Subtractive Synthesis?

Moving away from the rich, layered world of additive sound synthesis, we find ourselves in the holy realm of subtractive synthesis, a synth language that has shaped the sounds of countless records.

While additive synthesis builds sounds by layering harmonics, subtractive synthesis takes the opposite approach.

You start with a harmonically rich waveform, such as a square, sawtooth, or pulse wave, and carve out frequencies using filters, LFOs, and envelope generators to shape and mold the sound. Think of it sculpting marble, where you remove material to reveal the form within.

Subtractive synthesis can take many forms, though it has long been celebrated for its warm, resonant sounds that it produces. One quintessential example of subtractive synthesis at work is in the iconic track "Jump" by Van Halen. The song's memorable lead synth line was played on an Oberheim OB-Xa, which arguably became one of the most popular hardware synths of all time.

A History of Subtractive Synthesis

We can trace subtractive synthesis all the way back to the early experiments in electronic instruments.

However, the advent of subtractive analog synthesizers is often credited to the pioneering work of Robert Moog and Donald Buchla in the 1960s. Moog, in particular, played a crucial role with the introduction of the Moog synthesizer, which became synonymous with subtractive synthesis.

This instrument featured oscillators that generated rich, raw sounds, which could then be sculpted into a wide range of distinguished tones using filters, envelopes, and modulators. In many ways, it was Moog's synthesizer that brought subtractive synthesis to the forefront of music.

In fact, one of the earliest and most influential compositions that used subtractive synthesis was Wendy Carlos's "Switched-On Bach" in 1968. This a groundbreaking album reimagined Bach's compositions using Moog synthesizers and demonstrated the musical potential of electronic instruments, solidifying them as serious tools for modern music production.

While Robert Moog is often heralded for popularizing subtractive synthesis, Donald Buchla's contributions were equally pioneering, albeit with a different philosophy. Buchla was working on the West Coast of the United States around the same time as Moog, when he introduced the Buchla Box, an instrument that emphasized experimental sounds and complex modulation over the traditional keyboard interface favored by Moog.

Buchla's approach to synthesis and instrument design was deeply influential in the realms of avant-garde and electronic music. He'd go on to push the boundaries of what could be achieved with electronic music, though his works is perhaps less mainstream than Moog's.

As technology advanced, subtractive synthesis evolved with the introduction of polyphonic synthesizers in the late 1970s and digital synthesizers in the 1980s. These developments expanded the capabilities of subtractive synthesis, offering more complex waveform and sound design options. Plus, it facilitated its integration into just about every genre, from rock to pop to hip-hop.

How Does Subtractive Synthesis Work?

Subtractive synthesis is unique in that it begins with generating a rich, complex waveform, typically produced by an oscillator. This waveform, often a sawtooth, square, or pulse wave, contains a broad spectrum of harmonics.

Users can then take that raw sound and shape into something musically pleasing or interesting by subtracting certain frequencies . The primary tool for this task is the filter, which selectively removes frequencies from the sound. Low-pass filters, which allow frequencies below a certain cutoff point to pass through while attenuating higher frequencies, are especially common in subtractive synthesis. High-pass and band-pass filters serve similar roles, though they target different portions of the frequency spectrum.

Some other key controls in subtractive synthesis include envelope generators , which shape the amplitude of the sound over time, defining how it evolves from the moment a note is played until it fades away. Envelopes typically have four stages: attack, decay, sustain, and release (ADSR), allowing users to shape them in a multitude of ways.

Low-frequency oscillators (LFOs) also offer modulation capabilities, adding movement to the sound as a player modulates various parameters, such as pitch, filter cutoff, or amplitude, at a low frequency.

One of the reasons I prefer subtractive synthesis over additive for several reasons is that with subtractive synths, you often get a more intuitive and immediate response. Shaping sound by removing frequencies is a very hands-on approach, and getting warm, rich sounds that fit well in a mix can be done quickly, especially for basses, leads, and pads.

Plus, both hardware and software subtractive synths typically have user-friendly interfaces that encourages experimentation, making it much easier for beginners who are simply trying to grasp the fundamentals of synthesis.

Subtractive Synthesis in the Digital Era

While hardware subtractive synthesizers are definitely back in style, getting your hands on those tactile knobs and faders can be a pricey venture. Luckily, you can save some money and get a very true-to-analog sound with many subtractive software synthesizers that are out there.

Better yet, many subtractive software synths surpass their hardware counterparts in terms of flexibility, making them great for sound designers and those who like to experiment. Let's check out a few of the best options.

Xfer Records - Serum

Serum has long been one of the best software synths out there. Not only does it have some of the cleanest and most flexible oscillators of any synth VST I can think of, but it also provides endless modulation options and an intuitive visual interface that demystifies complex sound design processes.

What sets Serum apart is its wavetable synthesis capability. You can seamlessly morph between a vast array of waveforms—not just the classic sawtooth, square, or sine waves typical of subtractive synthesis. This flexibility, combined with a powerful dual filter section that can process sounds in serial or parallel, allows you to generate sounds ranging from subtle pads to wobbling basses and beyond.

The drag-and-drop modulation assignment makes the process even simply, while the real-time waveform visualization provides immediate visual feedback. In many ways, it's also an educational tool! As the cherry on top, you get a high-quality effects rack, which include reverb, delay, and distortion, giving you all the tools you need to add the finishing touches to any sound.

Native Instruments - Massive X

Massive X is a heavyweight in the subtractive synthesis category, and has earned its reputation over the years with its signature "fat" sound and extensive modulation capabilities. The first iteration of Massive was single-handedly responsible for some of the biggest EDM hits of the early 2000s.

Native Instruments designed Massive with a focus on producing the rich, deep basses and soaring leads, many of which have become staples in electronic music. Its unique approach to routing and modulation, where virtually any parameter can be modulated in a drag-and-drop fashion, offers unparalleled creative freedom.

With the performers and stepper modulation sources, you can transform static sounds into evolving, rhythmic textures. Plus, the synthesizer’s oscillator section is capable of producing both classic analog waveforms and intricate digital timbres, so no matter what kinds of musical sounds you're after, Massive can deliver. It's a go-to for anyone making electronic music.

LennarDigital - Sylenth1

Sylenth1 might feel a bit dated to some, though in terms of software synth legendary status, it deserves all the love it can get.

It has a very clear, digital sound and an endless array of patches and presets that you can use to dial in just about any tone you can dream up. Even so, it beautifully emulates the subtle imperfections of hardware oscillators and filters, giving it a life-like quality.

Sylenth1’s architecture features four oscillators, two filter sections, and an array of modulation options, allowing for a wide range of sounds. With a streamlined and focused user interface, it's just as accessible to beginners as it is exciting for experts.

Final Thoughts

Most synth users that I know don't have a serious preference between additive and subtractive synthesis, as they're both useful in certain situations. I'd recommend trying out some of the VST options above and experimenting to figure out what suits you most!

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