What is FM Synthesis & How Does It Work?

What is FM Synthesis & How Does It Work? What is FM Synthesis & How Does It Work?

FM Synthesis is the sonic architect behind some of the most iconic tracks of the 80s and 90s. In many ways, it revolutionized music production with its distinctive and eclectic sounds.

From the electric buzz of distorted bass lines to the crystalline shimmer of digital bells, FM synthesis laid the foundation for a new wave of music. However, to many aspiring producers, FM synthesis can feel complex and overwhelming, especially once you start digging into the intricate web of modulators and carriers.

But fear not! as in this article, we're going to demystify FM Synthesis, break down its components, and explore a few different options for hardware and software synths you can add to your arsenal today.

What is FM Synthesis?

FM synthesis is short for frequency modulation synthesis.

At its core, it involves the modulation of one waveform's frequency (the carrier) by another waveform's frequency (the modulator), creating complex harmonic and inharmonic sounds that are both rich and dynamic. The interplay between the carrier and modulator can produce a vast range of timbres, from natural-sounding instruments to entirely novel, digital sounds that are hard to categorize.

The process starts with the carrier, such as a simple waveform like a basic sine wave, which by itself sounds pure and unassuming. The modulator, another waveform, then alters the frequency of the carrier, introducing new frequencies called sidebands . The frequency and amplitude of the modulator determine the character and intensity of the resulting sound. By adjusting these parameters, along with the modulation index , you can generate a wide spectrum of sonic textures.

What makes FM synthesis particularly powerful is its ability to create complex sounds using relatively low amounts of computational power. This is one of the reasons it was so popular in digital synthesizers of the 1980s. Despite its technical complexity, you can open up a world of sound design possibilities when you understand its basic workflow.

The Components of FM Synthesis

To fully grasp the magic of FM synthesis, you first have to understand its key components, each of which plays a distinct role in shaping the final sound. From the operators that act as the building blocks of FM tones to the dance between carrier and modulators, there are several elements that come together to create the sounds FM synthesis is known for. Let's dive deeper into each!


FM operators are the fundamental sound-generating components in FM synthesis. These essentially function as individual analog oscillators. Each FM operator can act as either a carrier, producing audible sound, or a modulator, influencing the frequency and, consequently, the timbre of the carrier signal.

Operators generate basic waveforms - like sine waves - which can then be modulated to create more complex sounds. However, the true power of FM synthesis lies in how these operators are interconnected and modulated. As a result, you get access to a vast array of sounds.

Carriers and Modulators

The "carriers" and "modulators" refer to the roles that operators can play within the synthesis process.

Carriers are the operators that produce the actual sound you hear, which serves as the fundamental audio signal, while modulators do not produce sound directly audible to the listener. Instead, they influence or "modulate" the frequency of the carrier, thereby altering its harmonic content and timbre.

The interaction between these two is what generates the complex sounds found in FM synthesis. When you vary the frequency, amplitude, and the modulation index of the modulators, you can create everything from subtle vibrato effects to dramatic changes in the sound's harmonic structure.


I like to think of FM algorithms as the blueprints that dictate how operators are interconnected. Each algorithm represents a specific operator configuration, determining the pathways through which they influence each other.

Essentially, algorithms define the modulation structure, outlining which operators modulate others and in what order the interactions occur. This structural framework is key, as it directly impacts the timbral possibilities. Different algorithms can produce vastly different results using different styles of modulation routing, even with the same set of operators.

Envelope Generators

Next, we have envelope generators, which are there to shape the dynamic contour of a sound over time. They determine how the amplitude of both carriers and modulators changes from the moment a note is triggered until it ends, which influences the overall expression and movement of the sound.

Envelop generators typically use ADSR parameters - Attack, Decay, Sustain, and Release - for precise control over how quickly a sound reaches its peak volume (Attack), how it decreases to the Sustain level, and finally, how it fades out (Release).

By using envelope generators in FM synthesis, we can not only sculpt the volume envelope of the sound but also dramatically alter the timbral characteristics throughout the duration of that sound.


The relationship between the frequencies of the carrier and the modulator signal is defined by a frequency ratio, and it's this ratio that determines the harmonic or inharmonic nature of the sound output.

When the ratio is made up of whole numbers (such as 1:1, 2:1, 3:2), you get harmonic and musically consonant sounds, which often resemble traditional musical instruments. These are sounds where the frequencies of the produced overtones are integer multiples of a fundamental frequency.

On the other hand, when the ratio involves non-integer relationships (such as 1.5:1, 2.7:1), the outcome is inharmonic and often more percussive or bell-like sounds, which are musically dissonant. These inharmonic sounds do not have overtones that are integer multiples of a fundamental frequency, which is why you often get more complex tones or metallic FM sounds.


Feedback occurs when the output of an operator (essentially a sine wave generator in this context) is routed back into itself. This process creates a more complex waveform, introducing additional harmonics or overtones to enrich the sound's texture.

It's worth noting that feedback is most commonly applied to a modulator. When an operator modulates its own frequency through feedback, it alters its waveform shape, moving from a simple sine wave to a more complex form. This complexity adds harmonic or inharmonic content to the sound, depending on the amount of feedback applied.

As a result, you can get an array of complex timbers, from thick leads to aggressive, distorted basses. It's also a great tool for sound designers who want to create evolving tones.

A Brief History of FM Synthesis

FM synthesis owes much of its development and popularization to the work of John Chowning . In the late 1960s, Chowning, a composer and researcher at Stanford University, began exploring the potential of FM synthesis as a means of creating complex sounds.

His groundbreaking discovery - that modulating the frequency of one waveform with another could produce a wide spectrum of both harmonic and inharmonic sounds - laid the foundation for FM synthesis. This method was not only innovative but also highly efficient, making it suitable for digital implementation. Chowning's work ultimately led to Stanford University licensing the technology to Yamaha, which marked the beginning of FM synthesis's commercial journey.

The Yamaha GS-1 was introduced in 1980 and was the first commercial FM synthesizer to make its way into the music industry. However, due to its size, complexity, and cost, the GS-1 was accessible to only a handful of musicians and studios.

This exclusivity changed with the introduction of the Yamaha DX7 in 1983. The DX7 utilized Chowning's FM synthesis principles, though it was groundbreaking in terms of its sound capabilities, affordability, and portability. Its sounds were incredibly distinct, offering that bright, rich, digital-sounding timbre that was a staple in the music of the 1980s, especially in pop and rock.

In many ways, the introduction of this FM synth marked a significant shift in the music production landscape, encouraging the adoption of digital synthesizers.

Of course, the legacy of FM synthesis did not stop with hardware.

As the world transitioned into the digital age, FM synthesis found a new life in the form of VST (Virtual Studio Technology) plugins. These software synthesizers emulate the sound and functionality of traditional FM synthesizers while offering expanded flexibility and integration into DAWs.

Today, FM synths are still evolving, providing musicians and producers with an ever-growing toolkit for sound design.

Hardware FM Synthesizers

Hardware FM synthesizers made a splash in the 1980s, and some of the models became classic FM synths that are still very much in use today. Let's take a look at some of the most iconic pieces of FM gear.

Yamaha DX7

As we've already discussed, the Yamaha DX7 is somewhat of a monumental figure in FM synthesis. In many ways, it was this FM synth that heralded the widespread adoption of frequency modulation synthesis in music production.

The DX7 hit that market in 1983 and transformed the landscape with its clarity, complex harmonics, and endless sonic possibilities. Musicians loved it for its unimaginable palette of sounds, including the electric pianos and basses that defined the 80s' pop sound. Today, we can still hear those dreamy pads and piercing leads in synthwave music.

The true beauty of the DX7, however, was its interface, which featured a modest number of buttons and a single data slider. This marked a departure from the knob-laden analog synths of its time, challenging musicians to explore sound design in new ways. Despite its learning curve, the DX7 was still a relatively efficient synth. With its deep programming, it offered unparalleled creativity at the time.

Even today, it's one of the most durable and reliable classic synths, which is why it became a staple in studios and on stages around the world.

Elektron Digitone

The makers of the Elektron Digitone took a modern twist on traditional FM synthesis, blending the complexity of digital sound generation with the intuitive workflow for which Elektron is renowned.

Released in the late 2010s, this compact digital FM synth reimagined FM synthesis, making it more accessible and musically expressive than ever before. Unlike many other FM synths, it was made with a sleek, user-friendly interface and robust build. The first time I played with one, I was surprised how easy it was to dial in different sounds without the steep learning curve often associated with FM synthesis.

At its core, the Digitone features a powerful 4-operator FM engine, complemented by Elektron's signature step sequencer, allowing users to dial in intricate rhythmic patterns and sequences. It takes more of an innovative approach to FM synthesis by simplifying the modulation matrix and offering hands-on control over sound shaping.

Getting into the sound design muck with this synth is a far more intuitive process than you'd expect, and with the inclusion of multimode filters and effects, you get a nice warmth and depth that acts as a counterbalance to the potentially cold precision of digital FM sounds.

Beyond the fact that it shines as a standalone instrument, its MIDI and Overbridge capabilities ensure it fits beautifully into any setup, bridging the gap between hardware and software music production environments.

Korg Opsix

The Korg Opsix was a huge leap forward in the evolution of frequency modulation synthesis. It married the depth and versatility of traditional FM sound generation with a level of accessibility and hands-on control not typically associated with FM synths.

Introduced in 2020 amidst a seeming world collapse, the Opsix was a bright light for FM synthesis and hardware synth fans in general. It made digital FM synthesis more approachable for a wide range of users without sacrificing the sonic complexity that makes it so revered.

One of the standout features of the Opsix is its innovative interface, which includes a detailed OLED display and an array of knobs and sliders that offer immediate tactile control over parameters. I love a tactile synth that's easy to navigate, as it makes dialing in complex timbres a much more intuitive process.

Beyond traditional FM, the Opsix expands its palette with a hybrid approach that incorporates wave shaping, filtering, and effects. You can create a much broader spectrum of sounds, from crystalline bells to evolving pads.

The Opsix also shines in its ability to go beyond the classic 4-operator or 6-operator setups, offering an "altered" FM mode that introduces new operator modes and modulation options. Its polyphonic sequencer, motion sequencing, and arpeggiator make it an absolute powerhouse for both studio production and live performances.

Software FM Synthesizers

Software dominates the market in music production these days, and thanks to the many great brands and developers, there is an array of killer software FM synths to choose from.

Native Instruments FM8

Native Instruments' FM8 has become somewhat of a titan in the landscape of software FM synthesizers. Since its introduction as FM7 in 2002, it has been renowned for its sophisticated depth and flexibility.

Built upon the rich heritage of FM synthesis, FM8, going on 18 years old, offers a relatively modern twist with a user-friendly interface and endless sound possibilities. It expertly combines the intricate, harmonic-rich textures characteristic of FM synthesis with a contemporary design that streamlines the programming process, making it accessible for all kinds of users.

It was one of the first software synths I ever got my hands on and I still use it to this day.

At the heart of FM8 is its powerful sound engine, which is more than capable of producing everything from warm, classic bell tones reminiscent of vintage FM synths to cutting-edge textures and leads that push the boundaries of digital synthesis altogether.

The matrix display might feel a bit outdated at this point, but with the massive library of presets, you always have a good starting point to start exploring.

Waves Flow Motion

Waves Flow Motion might be one of my favorite software synths to come out in the past decade. There's just something about the grit and edge you get from the FM sound that's hard to find elsewhere.

It beautifully blends traditional FM synthesis techniques with a visually engaging and highly intuitive interface. One of the ways in which Waves was able to distinguish this synth was by offering users an immediate and hands-on experience. If you didn't see the theme of this article already, FM synthesis can often feel complex and inaccessible, which is why I'm a huge fan of software that simplifies the process.

The innovative graphical interface makes it easy to create, connect, and manipulate FM sounds, and see different components of those sounds evolve in real-time using dynamic visual feedback.

With so many great presets, Flow Motion allows you to quickly find whatever sound it is that you hear in your head. You get four flexible FM oscillators with a versatile modulation matrix and an array of onboard effects, offering endless inspiration, no matter what kind of music you make.

I never really thought of Waves as a VST instrument designer, and in many ways, Flow Motion changed all of that for me.

Arturia DX7 V

Whether you're lacking the funds or the studio real estate, it doesn't mean you can't get your hands on the sounds of one of the most famous FM synths of all time.

The Arturia DX7 V is a meticulous digital recreation of the iconic Yamaha DX7. It brings all the quintessential sounds of FM synthesis sound into the modern production with remarkable authenticity (as with many Arturia products).

Like the company does with all its synth emulations, Arturia has gone to great lengths to ensure that the DX7 V not only emulates the distinctive sonic characteristics of its hardware predecessor but also expands upon it with new features that cater to today's music production workflows.

With its intuitive interface, the DX7 V breaks down the original DX7's notoriously complex programming barrier, offering users a more accessible way to explore and create sounds. With the added modulations matrix, new oscillator options, and built-in effects engine, the DX7 V significantly broadens the sound design possibilities beyond what was possible with the original instrument.

You can now easily navigate through layers of FM synthesis and create just about any sound your heart desires in what feels like an instant.

Final Thoughts

Frequency modulation is a complex beast, and I can only hope that this short guide has made it feel a bit more accessible for you. From the foundations laid by John Chowning's pioneering work to the software innovations that continue to push FM synthesis into new creative territories, it's a style of synthesis that is well worth exploring.

Whether you're arranging your next synthwave hit, designing sounds for a blockbuster film, or simply getting your feet wet with a new FM synth, there is so much to explore! Have fun and get experimental.

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