FM Synthesis – An Introduction

If you work with or plan on using an FM synthesiser, it’s important that you have at least an introductory understanding of what FM synthesis is.

While the theory underpinning this type of synthesis is a bit technical, it can be broken down into different sections to help you understand just about everything you need to know. Armed with a more thorough understanding, you’ll be able to create new and unique sounds during your mixing, music making and DJing.

Let’s begin and dive head first into the world of FM synthesis. 

What is FM Synthesis?

FM synthesis stands for Frequency Modulation Synthesis. While the name might sound technical as well, the truth is it’s quite appropriate. FM synthesis occurs when the waveform of a sound is modulated (i.e. changed) by manipulating the frequency. We do that with what is called a ‘modulator’.

This modulator is a signal that modulates the pitch of another signal. This is called the carrier. The modulator and carrier need to be in the same or a closely related audio range. We’ll dive more into this a little later on.

The resulting sound from FM synthesis has an all-new frequency.

Where Does FM Synthesis Come From?

Back in 1967, a gentleman by the name of John Chowning was experimenting with complex audio waveforms. He was using the waveforms to module the pitch of non-complex waveforms and in doing so began to create audio signals with extremely increased frequencies. 

As Chowning continued to experiment with harmonics and modulated waves he realised that by changing the frequency of the signal, he could create new and different sounds.

From there, the first FM synthesiser was created in the form of the DX7, produced by Yamaha. Since then, FM synthesis has been employed in a variety of ways throughout the DJing world.

Understanding FM Synthesis

Why use FM Synthesis?

In short, FM synthesis is a useful technique that can help produce a distinct set of sounds. By modulating a sound by using another sound, DJs and music creators could expand what was possible in their art and exercise maximum creativity. 

FM synthesis works particularly well for complex attack instruments (think: electric pianos), aggressive bass sounds, distorted sounds, plucked strings and the like. 

How do you use FM synthesis?

As we mentioned above, FM synthesis is based on frequency modulation to create new sounds. By adding movement to a basic oscillator waveform you can make more interesting and unique sounds. 

For example, using a low-frequency oscillator on an oscillator frequency will produce a simple type of FM, known as vibrato. Now increase the frequency of that same sound more and more, and you’ll begin hearing an all new sound. As the frequencies reach a certain level, the modulation produces timbres that are unique to FM synthesis. 

By the way, the term timbre refers to the overtone quality of a particular sound.

Breaking Down the Components of FM Synthesis

Operators

Operators are integral to the process of FM synthesis. In a way, you can consider operators as the foundational building blocks of the entire process.

The four parts that make up an operator are:

• The input
• The oscillator
• The amplifier
• The output

This group of components are what interact with each other, enabling the set up of the synthesis itself. Moreover, it’s not just the operators that interact, but the groups of operators as well.

If you’re struggling with this, consider each individual operator to be its own small synthesisier with its own respective oscillator and a basic sine wave oscillator shape. 

The particular arrangement of the operators and groups of operators are what determine and distinguish the sound output. Most common synths have six operators in total. Though some newer models use four operators. 

DJs often use a MIDI input to control the oscillator’s pitch, though there are alternative ways as well. 

Carriers and Modulators

In its most basic forms, a frequency modulation is dependent on there being two (or more) sound sources. The one sound source is the one being modulated, and the other one is the one doing the modulating.

When it comes to FM synthesis, the operators act as both the modulator and modulated. 

The term modulator is easiest to remember as it does the modulating. Hence, the term. 

The one being modulated is called the carrier. 

Amplifiers

The level of signal coming from the oscillator is called the amplifier. Using an envelope generator, you can change the signal level over a period of time and create a wide variety of different sounds. 

Using Operators

The way in which you create sounds is by arranging the four or six operators of your standard synth into a sequence called an algorithm.

Different programs work differently but most will come with pre-set algorithms and allow you to create custom ones as well. If you use the Ableton software, for example, you’ll be able to do this in the Operator functionality. Alternatively, you can use the FM8 synth from Native Instruments. 

Most synths operate with the same principle. Each operator is indicated on the display and has an attached oscillator. Using the right controls, you can then change the pitch of the oscillator to whatever level you so choose. A separate control will allow you to control the in-built amplifier and another feature (called the Global Shell on Ableton) will bring up a display to customise the algorithm. 

Playing around with these different controls and features will enable you to use FM synthesis to create original and fantastic new sounds. 

A Last Word on FM Synthesis

Like all sorts of DJ techniques and sound effects, the more you play around and explore the quicker you’ll find what works for you. Start with the preset algorithms first before moving into the customisation options. 

If you found this rather technical guide a little confusing or you want some more FM synthesis related tips, make sure to give us a call today on 1300 352 489. The DJ City team is here to help you with all your FM questions no matter how specific or technical.