Let’s Learn: Frequency Modulation Synthesis

In this article, I will try to explain the basics of frequency modulation synthesis using plugin FM8. Altough very complicated and not so logical like subtractive synthesis, where you take sound from the osciliator and cut off frequencies you don’t want to hear, frequency modulation is doing exactly opposite thing. You add up parts of spectrum using modulators (or operators), which results with more unique, but also darker kind of sounds because of its complex waveforms that are distorted. That’s why it is so popular in Bass music, because it’s easy to achieve dark vibe with it.

History of FM

Frequency modulation is mainly used digitally, because pitch in analog gear wasn’t stable. First most popular instrument was DX7 by Yamaha, one of the most popular synth. It was actually pretty hard to program, but rewarding. Sound that was getting out was very metallic and analog because of thickness it had. Most popular FM software instruments are FM8, Sytrus and Operator. Altough I will use FM8 you can apply this tutorial to any FM synth. But unlike subtractive synths, frequency modulation synths are very unique and each to their own. It takes time to master each of them and understand their power which lies in endless options.

Basic Principle

In FM8 we have 6 Operators in Matrix (A, B, C, D, E, F, I will explain X and Z later). We are going to divide them in carriers and modulators. Now, when you start up FM8 and press expert mode, which is most important mode here, you can see F is being routed out. That means it will act as a carrier, because it carries the sound out of the synth.

So, currently, F is carrier. if I route for example B out, it will also become a carrier. But, now I will route operator E in F. That means operator E will act as a modulator, modulating operator F and adding frequencies, while F carries the sound out. I will also route B into F and that means B is now a modulator, but also still carrier. Now we got 3 operators, F which acts as carrier, E which acts as modulator, thus changing the shape and sound of carrier, and B which acts as both.

Perhaps, when things are a bit cleared up with modulators and carriers, you can see how many options there are when using FM. We will now move onto waveforms, offset and ratios, which can be edited for each operator separately. So let’s click on F.

Waveforms in FM8 aren’t really regular waveforms, they are more of a shape in which operator will modulate. Offset and ratio both affect pitch, but differently. Offset will affect exact frequency you’ve set, while ratio uses ratio system. Increasing it by 2 will pitch up sound by octave. Now double the value. You get 4, and that is a ratio which will pitch up sound by two octaves. Ratio 8, three octaves and so on. Little bit lower, you can find envelope that will shape or modulate the amplitude (value in matrix).

Now imagine the possibilities in FM8. Let’s take a look at X and Z now. X is a noise operator, and Z is a filter. Altough, earlier versions of frequency modulation synths didn’t include filters, FM8 has one. By routing operators into them and routing X and Z out, you can get some interesting variations in sound.

FM8 also includes pitch section, which can be used to set up the pitch and modulate it. It’s pretty usefull when creating short wacky stabs, or long rolling basslines to keep them interesting.

In envelope section, you can automate the volume of each operator and master sound.

You can see arpeggiator which FM8 also includes and effects, which can be used to save a bit of CPU or if you like to do everything in your synth. In master section, you can change some basic parameters like pitch, portamento and volume of your patch.

And that’s pretty much everything to get you started in FM8. It isn’t so complicated but takes time to learn and understand. Only disadvantage when using FM8 is that you can’t add your harmonics, or draw your own waveforms like in sytrus and operator. But still, it’s very powerful and rewarding, it will take your production to the next levels and you tunes will definetely sound diferent. Also be careful because it is very easy to mess up a patch in FM8 by turning on some parameters too high.All that is left now is some experimenting. Thanks for reading and hope you’ve learned something.