A Bluffers’ Guide to Frequency Modulation

There’s a whole variety of synthesis types available ranging from things you’ve probably come across like subtractive, wavetable and granular to lesser known techniques like additive, phase distortion, Karplus-Strong and vector. For the longest of times I had thought Frequency Modulation was only capable of making thin and papery computer game sounds, cheesy brittle electric pianos and laughably cheesy marimbas. How wrong was I?

Yes frequency modulation (FM) has been around for a long time, and yes it’s the same thing we use(d) to transmit radio signals with. It is responsible for some drab patches that were totally rinsed during the 80s and yes it can be quite complicated BUT it’s also capable of some incredibly rich and kinetic sounds. FM has just had bad PR.

This is an article I hesitated writing for ages because each time I drafted it I found another excellent resource to include and while I want it to be comprehensive I want it to be understandable by someone with little to no previous experience with FM before.

There is a lot of content about FM synthesis out there both on blogs, YouTube and education papers and here I want to collect what I consider to be the best bits in one place while offering some (hopefully) original insight and keeping the content suitable for users of all abilities.

What is Frequency Modulation?

Before diving into the synthesis side of things, let’s first clarify exactly what frequency modulation is and what it has been used for historically. Older readers might remember the days before digital radio when FM and AM (amplitude modulation) were the de facto way of listening to radio stations. But what is frequency modulation? Wikipedia describes it as the…

…encoding of information in a carrier wave by varying the instantaneous frequency of the wave.

Confused how you can encode signals on to one another? Here’s a quick description from Techquickie. I’ve embedded from 2.26 where the presenter talks specifically about FM radio but you can rewind if you want to learn about AM too.

While this clears up some of the fog, I found this public broadcast video from the Department of Defence from 1964 a little more helpful in explaining exactly what’s going on. Naturally it goes into a little more detail however at just short of 30 minutes I would understand if you just précis it by skipping through. A lot can be skimmed from this but it’s not all entirely relevant to musical applications. Worth a watch if you want a more holistic understanding.

Frequency Modulation Synthesis

I’ll admit that FM was something I struggled with for a long time, even with a medium-to-good grasp of subtractive synthesis I couldn’t really get my head around the sonics of this.

The easiest way I’ve began to understand FM is comparing it to a simple vibrato sound. Vibrato is an effect employed by singers, guitarists, other string instrumentalists and others. It’s a subtle modulating of the pitch. Jazz and opera singers are masterful of using this technique to add some shimmer to longer held notes.

It’s commonly found on synthesisers too, with a modulation wheel or similar adding vibrato to sounds. But how do we patch it? It helps if you have an at least rudimentary understanding of the signal path of an analog synth to get this so read this if you don’t.

We route an oscillator to an amplifier (or, VCA) and take a low frequency oscillator (LFO) and modulate the oscillator’s pitch. Simple as that.

LFOs are sub sonic and therefore inaudible. They typically range from between ~0.01 and 20 Hz. Depending on the amplitude (volume or wave strength) of the LFO, the original tone or pitch can still be perceived at lower amplitudes with the vibrato straddling it, moving slightly above and below.

The more you increase the amplitude the more the sound strays from a vibrato and moves closer to a laser-like sound, with the pitches either side of the original pitch becoming further and further apart. Here’s a quick (two minute) explanation of frequency modulation using eurorack modular to demonstrate a quick patch.

For a little more of an eloquent and romantic summary, here’s John Chowning, credited as the father of FM synthesis explaining a little about how he discovered a musical usage for the technique:

Let’s try and visualise what’s happening here. I’m using Native Instruments Reaktor as it has this flow chart-like architecture than can help you imagine the signal and modulation passing through the synth.

In the below example we have a 1 Hz LFO controlling the pitch of a sine wave (single harmonic waveform) and the amplitude of the LFO is being turned up slowly. At first we hear a subtle undulation and as it increases the LFO creates a sound more akin to a dub siren.

As we gradually increase the rate of this LFO from 0.01 Hz up to around 11 Hz, it becomes harder to hear the nuanced changes in pitch. At slower rates we can still easily count the cycles and even determine the underlying note pitch but as the amount of modulation and speed of the modulation increases it becomes harder to hear the original tone.

Eventually as the LFO approaches audio rate (> 20 Hz), and the original tone becomes almost imperceivable. This creates a series of complex additional harmonics – this is frequency modulation. In the example below, our LFO rises from 11 Hz to 100 Hz:

Whilst this is FM in a nutshell, is it musical…? The pitch of an oscillator is tracked by our keyboard input, meaning it responds to changes in pitch when you go higher or lower down the keyboard. However our LFO is static, as the frequency is fixed. Yes we can change the rate of the LFO manually but it has no relationship to the keyboard and therefor has an arbitrary relationship to our oscillator. Let’s play a basic major scale and hear how the LFO at a rate of 100 Hz effects each note:

Some notes don’t sound too bad – for example the 2nd, 4th and 7th notes sound quite pleasant to my ears but the rest sounds almost accidental and quite grating. This is why FM synthesisers have different interfaces for tuning oscillators compared to an ordinary subtractive synth but we’ll get to that later when we start looking at specific examples.

*edit 2018* YouTuber and musician ANDREW HUANG has recently contributed a fantastically short but powerful What the F is FM Synthesis:

Logic’s EFM1

Before getting into operators and terminology more commonly associated with frequency modulation techniques nowadays, I want to start with the concept of carriers and modulators – as this is how I learnt about FM, through Logic’s EFM1.

You may have come across carries and modulators with ring modulation or vocoding, and you can still find some more basic FM synths that use this terminology. For a small interface and just two oscillators with minimal modulation capabilities, the EFM1 packs quite a punch, and for that reason it’s a great place to start.

Let’s begin with some basics. The carrier oscillator is routed to the amp/output and produces a sine wave. With FM it’s quite easy to create brittle, bright, metallic and hollow sounds by just modulating sine waves.

The modulator oscillator isn’t connected to the amp/output and is actually connected to the carrier much like the LFO was in our vibrato example, only the difference is the modulator oscillator is tracked by our keyboard input. Changing specifics of the modulator oscillator’s pitch, volume or harmonic content will in-turn affect the timbral qualities of our carrier.

In EFM1, both the carrier and modulator use Harmonics to tune rather than more conventional octaves, tones and semitones. We also have a bi-polar fine tuning control (in cents, or 100ths of a semitone) for a more ordinary detuning effect. Lastly we have a button to fix the frequency of the oscillator which is useful for drones, risers, drum synthesis or other FX.

But hold up… why do we tune is harmonics and not normal intervals? For the longest of times this stumped me. Let’s clarify first what harmonics are first. Harmonics are whole number ratios of a frequency obtained by multiplying the note by an integer.

That might sound more complicated than it is, but it’s really not. It’s quite simply multiplying a frequency by whole numbers such as 1, 2, 3, 4 and so on. They appear naturally in the Harmonic Series and are the building blocks of western harmony. They also have an intrinsic link to our intervalic system. Doubling the ratio from 1 to 2 will raise the pitch by an octave, doubling that again to 4 and in turn 8 would raise it by octaves again and again. Halving the ratio from 1 to 0.5 would drop the pitch by an octave.

But what about the ratios that aren’t 1, 2, 4, 8, 16 etc? These produce other harmonious intervals; multiplying by 3 would produce an interval close to a and octave plus a perfect fifth and multiplying by 5 would be an interval close to a two octaves plus a major third etc.

The reason we use use ratios is that they are mathematically pure compared to our equal tempered (12-tet) system of tuning we use in western music. In equal temperament we divide the octave in to semitones using the ¹²√2 – as there are 12 semitone in the octave, each semitone is 1 x¹²√2 higher than the previous. However the ¹²√2 is an irrational number and deviates slightly from the perfect ratio system.

While it’s possible to find some FM synths that can use equal temperament the sound produced by using the harmonic series tends to be more sonorous to our ears. I would strongly suggest familiarising yourself with harmonics in general as they crop up in lots of different areas of both music and music tech.

So do we blindly pick ratios? Well yes and no, and that really comes down to your experience with FM and a healthy dose of intuition. Below is an excellent (albeit slightly dated) video that explains a little bit about what to expect from certain ratio combinations.

The video is embedded from where the topic is picked up but watching the whole thing is not only great revision for frequency modulation in general but also contains a very comprehensive guide to subtractive synthesis at the start.

As you saw, the FM section of the video is focused around the legendary DX7 (more on this later) and some while some of the patch examples might sound a little sterile to our 2017 ears, the theory is top-notch and it’s well worth spending some time this video.

Anyway, back to EFM 1. Here’s our carrier in isolation with the harmonics slowly being turned from 1 up to 36 and then back down again. It should be a sound you are familiar with as it the harmonic series appears in nature:

The FM knob in the middle (unsurprisingly) controls that amount of frequency modulation on the carrier via the modulator. Here it is being turned to maximum and them down again with the harmonics of both oscillators set to 1:

The modulator on the left has the same harmonics and fine tune control as our carrier but also has a basic wavetable index. This scans through a small selection of interpolated waveforms containing different harmonic signatures which produces a whole range interesting timbres when modulating our carrier.

Let’s modulate the harmonic, fine tune and wave one by one, hearing how each in turn affects our carrier’s sound. I’ve left the FM dial at around 12’o’clock:

Here are some example patches I knocked up to demonstrate some of what this synth can do starting off with a simple retro bass sound synonymous with a lot of commercial UK house music at the moment. The sound is achieved by using envelope modulation to increase the FM amount at the front of the sound (no attack, short decay, no sustain), giving it a percussive transient knock. What’s really happening is just amplitude modulation – but it’s the amplitude of the modulation oscillator:

Here are some metallic, shimmering bells. The in-built unison adds that sheen and sparkle. Again there’s envelope modulation and some inharmonic detune between the oscillators from the ‘fine’ control. There are no spatial or time-based effects applied to this:

Next up is a soft, ethereal pad. I love FM for these types of sounds as you can start with sine wave and gradually shift their timbres into something kinetic, glassy, warm, cold, whatever. Even with just two oscillators there’s a lot going on:

Last off is an industrial-like drone. Atonality is relatively simple with FM while these types of sounds might be near impossible at best a struggle with subtractive synthesis:

As you can hear there’s a huge plethora of sounds available and considering this is a dead simple synth with limited functionality, you can begin to imagine what’s possible with more modulation capabilities.

So what’s actually going on here? Subtractive synthesis takes harmonically rich geometric waveforms such as sawtooths, pulses and noise and uses filters to attenuate their harmonics. FM works in the opposite manner starting with basic waveforms and increasing their complexity. The additional overtones created you can hear are called sidebands. Let’s have a look at what they are.

What are Sidebands?

While we could just brush over exactly what sidebands are I think to do the topic of FM justice it’s useful to talk about what they are. This might get a little abstract for some readers but just remember it’s not key to understand everything in immaculate detail, but you can do no harm by being on at least nodding terms with it.

So what are sidebands? Sidebands are the bi-product of frequency modulation and we actually get sidebands in other processes such as ring modulation and amplitude modulation. These are the additional frequencies produced by modulating two waveforms together at audio rate. Wikipedia describes them as:

…band[s] of frequencies higher than or lower than the carrier frequency, containing power as a result of the modulation process. The sidebands consist of all the Fourier components of the modulated signal except the carrier. All forms of modulation produce sidebands.

But how do we calculate them? And do we need to? One of the better definitions I’ve heard is from this video by YouTuber and sound designer Composing Gloves. This playlist is a whole series on explaining the nuts and bolts of FM and it’s fantastic so well worth a watch. To paraphrase his explanation:

…sideband frequencies are equal to the carrier frequency +/- a number multiplied by modulating frequency.

It’s actually a little more complicated than that because the amplitude and phase of the waveforms will also make a marked difference but this is just a basic description without jumping too far into the maths, which is honestly beyond even me.

N.B It’s worth noting too that some synths are bandlimited while others allow aliasing and others have oversampling options. These will all have a direct affect on the upper registers of the spectrum potentially adding harmonic distortion or wave folding-like qualities to the sound, so listen out 💀.

In reality this information isn’t whizzing through my mind when I’m making sounds but there’s no harm in better understanding a process.

There are primarily two ways in which we can change the content of the sidebands and affecting our timbre. One is by changing the ratio combinations of our oscillators and the other is by changing the amplitude of those oscillators (sometimes called the modulation index).

I’ve lifted this .gif from an excellent imgur post I found on Reddit that neatly visualises the sidebands created from a 1 Hz carrier bring modulated in increments from 1 to 10 Hz.

As you can see that the sound starts off looking not too dissimilar to wave folding and we can see gradually the discontinuity in the wave increases. The further away from a sine something looks (generally speaking) the brighter or richer it will sound.

Here is an audio example I’ve made using EFM1 to try and demonstrate what the above .gif might sound like:

What does this mean practically? As a musician and not a mathematician this is tough for me to express but it’s actually an easy concept.

If we consider an example of just two oscillators for a second, the way I think about it is that the simpler the two numbers can be expressed as a fraction the more harmonious it will sound.

Ratio combinations of 1:1, 2:1, 3:2, 5:4, 4:1, 5:1, 6:1 etc will all sound relatively pleasant as they are simple rational numbers and the fractions have small(er) denominators when written in reduced form.

If we increase the complexity of the fraction introducing numbers further away from zero or further apart from each other, the brighter and potentially harsher the sound will become. Ratios such as 10:9, 11:10, 30:31 and so on will produce more complex sidebands.

Where it gets a little complicated is that we can actually accept a margin of error, much as we can with harmony. I mentioned before our 12tet system of equal temperament – none of the intervals contained within the octave are mathematically pure in relationship (except the octaves themselves) and by using the¹²√2 we get semitones that are slightly out of tune with each other. However, the margin of error is less than 10% so our ear accepts this.

Similarly with frequency modulation – if we took two operators with ratios of 2:1 and detuned them both ever-so-slightly, our ears wouldn’t hear 2.0792938:1.0542847 – we would naturally round it up as the margin of error is small enough.

Further Reading: I actually spoke to professor of physics at Nottingham University Dr. Philip Moriarty and Math YouTuber 3Blue1Brown about this topic to try and find a mathematically water-tight definition that was understandable by laypersons (such as me), and while we couldn’t exactly nail it, these resources were quite useful to me. Firstly this on instruments with non-harmonic overtones and this on music and measure theory.

In researching this subject I also found this mind-melting section from an old Future Music magazine (written by Robbie Stamp/Cyclick), the math is a little beyond me but it goes some way to explaining what we perceive to be dissonant .

So let’s think about what increasing the amplitude of our modulating oscillator does to our sound, or to put it more simply, increasing the FM depth. What happens when we increase that? Something else that resonated was this passage from an instruction manual on a eurorack modular unit called FM Aid by Happy Nerding. It explains:

By increasing the “FM [amount]” amount the user shifts additional harmonics proportionally further from the main tone, so the sonically perceived brightness of the sound and complexity increases too.

FM amounts at 0, 5, 10 dial positions and their respective spectrums. 100 Hz sawtooth wave is used as a Carried and Modulator. The whole manual can be found here.

The image on the left is lifted from a radio electronics site and it maps linear frequency on the x-axis and amplitude on the y-axis.

N.B Viewing frequency on a linear scale is useful for viewing relationships between harmonic. Spectral analysers like Voxengo SPAN and other use a logarithmic scale.

It shows how increasing the modulation index introduces more complex set of sidebands that eventually get spaced further apart from our fundamental tone.

If you still really want to push further with this, I would recommend having a look at this from the University of Indiana titled The Principles of Digital Synthesis.

I’ve linked from page 3 of the FM section. It’s a little bit beyond my comprehension so don’t feel it’s a requirement.

Ableton’s Operator

By far one of my favourite FM synthesisers is Ableton’s Operator. It neatly combines frequency modulation with elements of subtractive and even additive synthesis. It’s both compact and powerful and comes free with Ableton Suite. I find myself reaching for it over the Analog synth or any the other Ableton bundled instruments time and time again.

At this stage is worth confronting why FM synths tend to call their oscillators operators when they seem to perform a similar function. From my understanding it’s because while an operator can behave like an oscillator and produce a periodic waveform at a given pitch, it can also be used as a modulation source whilst also receiving modulation from another operator. Phew!

In EFM1, the routing of our two operators (the carrier and modulator) was fixed, but with Operator we can reconfigure how our four operators are connected, vastly expanding the sound palette available.

Operator is relatively simple once you get the hang of a few basic concepts and its interface. We have two sections either side of a dynamic display. This display changes depending on which shell you click, one of the four operators (A, B, C and D on the left), the LFO, filter, pitch information or global (right).

Below we are viewing the parameters for operator A. FM relies heavily on envelopes, and we can modify the basic ADSR parameters of operator A’s amplitude envelope as well as loop the AD portion, change our waveform (usual candidates here plus some more esoteric ones), restart phase and modify other parameters you might expect to find on an oscillator.

There is also an ‘oscillator’ tab within this display. This is the almost additive element of Operator – we can control the harmonic overtone content of our waveform. Changing these will instantly rename the waveform “user”. Below we are viewing a resolution of just 16 harmonics, but 32 and 64 are available too. This makes operator very powerful indeed.

Here are the four operators will using sine waves. The routing is D modulating C which in turn modules B which modules A. A is the only operator routed to the output. Hear how changing the amplitude (and tuning) of the other three operators changes the overall timbre:

Here I am taking a single harmonic and gradually adding additional harmonics above it. See and hear how it affects the sound:

N.B The clicks and pops you might be able to hear is what’s called zipper noise – it’s something that not designed to be modulated or automated, which is why it sounds clicky.

The bottom right shell is our global tab and that includes a fairly important element: the routing algorithm. This is that collection of pretty coloured squares in the top-middle of the display.

This is a visual representation of the routing of the four operators. The default is D > C > B > A, which means that only A is routed to our master. Additionally we can have D and C modulating B independently before they modulate A. On the very far right we have four operators without any frequency modulation capabilities. Let’s take four operators and record a low MIDI note, changing the routing for each example. Hear how drastically different they are when the modulation is in different orders and combinations:

You can learn more about FM synthesis routing algorithms in the below video. It mainly focusses on the DX7 (more on this later) but it neatly describes the types of routing algorithms, plus a little information on feedback modulation:

If you take into consideration Operator’s routing, additive capabilities, loopable envelope stages and everything else it has to offer, it’s a very useable, flexible and simple synth that (best of all) is free with Ableton Live Suite. I use it for kick drum layering, basses, pads, leads, metallic sounds, risers and a lot else. If you haven’t already I would recommend spending some alone time with it.

Electronic Musician recently published an excellent Operator masterclass which goes into much more detail than this article, so be sure to check that out.

AdLib SoundBlaster Technology

A sound that is very nostalgic to me is that of the DOS computer games I played as a child. Many of the sounds from games like Simon the Sorcerer, Day of the Tentacle and others used simple MIDI soundtracks that triggered the inbuilt chips in many commercially available computers, and more often than not in many situations it was the Yamaha YM3812, which I would hazard a guess that depending on your age may be some of the most familiar sounding FM tones you’ve ever heard.

This is an excellent video by the 8-Bit Keys parent channel 8-Bit Guy, archiving some of the keyboard that were available to buy that also used this chip or similar variations of it.

I loved this sound so much I wanted to see if anyone had made a software version and low-and-behold, they had. The image you see below you is a vst (sorry Logic users!) called JuceOPLVSTi and it’s FREE. Sonically it’s fantastic and I was instantly transported back to 1992.

The architecture is more similar to the EFM1 rather than Operator. It has limited polyphony, some unfamiliar waveforms on offer and the envelope works in a slightly peculiar way, but I really dig it.

WARNING: Sadly, my experience of this plug-in that whilst it sounds fantastic the OSX release seems very unstable and has caused Ableton to crash, and, in some cases cause irreparable damage to certain saves. There seems to be an issue with the buffer size of the project – it will plod along happily at 256 samples but either side of that I’ve not been able to stabilise it.

Here’s a selection of some of my favourite presets from it:

Riff:

Chords:

Italo Bass:

Pluck:

Native Instruments FM8

Next we come to an absolute beast of modern FM synthesis – Native Instruments FM8. I’m not claiming that this is the most powerful of all the FM synths out there but it would certainly stake a claim. As it happens little-known DnB knob twiddlers Noisia claimed if they were stranded on a desert island with just one VST it would be FM8 [paraphrased].

FM8 heavily borrows from Yamaha’s 1983 DX7, FM8 has the power of a monster six operators while having a visual layout that makes it very easy to program compared to its hardware predecessors. FM8’s modulation matrix is by far the clearest display of co-dependant modulation operators I’ve seen and that makes it a hugely flexible synthesiser.

N.B Interestingly enough the DX7 actually not actually a frequency modulation synthesiser and uses something called phase modulation, however sonically they are pretty damned similar.

I want to avoid doing an in-depth “this is exactly how to use every feature of FM8” tutorial as there’s already enough of those out there and I want focus more on what makes is special in the context of what we’ve looked at already. If you really want to get under the skin of this synth I would suggest checking out the official manual which is excellent in terms of quality. Let’s have a look at the layout:

Let’s look at the navigation on the left hand side of FM8. The ‘Browser’ and ‘Attributes’ tabs focus on preset management and the ‘Master’ tab deals with voices, unison parameters, pitch bend information and other global features. The ‘Effects’ tab is unsurprisingly just some effects (minor gripe here: FM8’s effects can’t have their order changed or be modulated, which sadly lets the synth down just a little, otherwise it’s great), and the ‘Arpeggiator’ is self explanatory.

The ‘Easy/Morph’ is a useful tab for making broad changes once you’ve programmed something. We’re looking at the ‘Expert’, this displays our modulation matrix (far right) and either information about our operators, envelopes, modulation, key scaling, pitch and a nice spectral analyser (always a winner with me).

The ‘Ops’ subsection of the ‘Expert’ tab we can see an overview of our six operators A to F. Here we can oversee their tuning as a Ratio (to four decimal places) and an Offset. The Offset allows fixed tunings perfect for linear frequency modulation or creating drums and drones when the Ratio is turned to 0.

We can select the operator’s waveform too – all of the usual candidates are here, sine, triangle, pulse, saw, but also tristate waves, combinations of harmonics, formants and some waves borrowed from the Yamaha TX-series of synths. Additionally here we can invert and restart the phase as well as modulate the pitch and amplitude.

If we click on one of the letters A to F we can see the Operators individual controls:

This is gives us a far-higher level of control including more amplitude modulation settings as well as pan position and a complex envelope stage. The envelopes in FM8 not only allow us intricate shaping of slopes from linear to exponential or logarithmic but we can also virtually do-away with LFOs by having loop-able shapes within the sustain stage.

Operators can be routed directly to the master output and/or to each other as well as self-modulating and there’s additional distortion and filter circuits (X and Z). As if that wasn’t enough it’s possible to route audio from your DAW straight into FM8 to either modulate with the operators or use as a modulation source!

The Matrix itself has a number of preset configurations that are included but it’s far more fun to experiment with your own. The default preset you will see that only operator F is routed to the master.

We first need to switch on other operators, do this by either ctrl + clicking on the operator or right click if your mouse allows. Let’s turn on operator E. Directly underneath operator E and to the left of operator F, click and drag up to increase the modulation.

If you press a MIDI note while doing this you will hear the amount of frequency modulation increase.

This is the maximum modulation you are setting. We can modify operator E’s amplitude envelope to shape that frequency modulation over operator F. By setting a long attack and decay with no sustain, the amount of FM will increase to a point and then decrease. Combing this with the other four operators and different waveforms and ratios can throw up some huge sounds.

What this really has over Ableton’s Operator is the ability to combine our six operators in any combination we want.

Below I’ve made a quick pad sound to show off the multi-stage envelopes in FM8:

All six operators are sent to the master. A and B are both parabolic waves (like soft clipped sines) tuned slightly sharp and flat of the third and fourth harmonic respectively. Using the offset allows us to add a detune that isn’t tracked by the keyboard. This can also function as a more traditional LFO but we wont be using that in this patch.

C and D are tuned (again slightly sharp and flat) of the third and second harmonics. These both employ the 1+2 and 1+3 waveforms. These are 1st and 2nd harmonics and 1st and third, so what we’re actually hearing is 2 x (1+2) equalling 2nd and 4th harmonics, and 3 x (1 + 3) resulting in the third and ninth. A and B are both tuned around the first harmonics and use simple sine waves.

Panning the operators around the stereo field gives us a far wider sound too. We can see A and B are modulating C and D, while C and D module E and F and E and F modulate A and B.

We can see that while all of the envelopes share long attack and release stages, the sustain portions all have differently curved shapes, creating LFO-like amplitude shifts in the frequency modulation. This gives the sense of cascading LFOs all out of sync with one another which has a natural and organic feel to it while feeling celestial and expansive (even if I do say so myself). This patch has no external reverb or effects on it. You can download it here.

FM8’s capabilities go way beyond floaty pads and nice sheeny sounds like that – it’s capable of searing tear-out DnB reese basses, trance arpeggios, thick analog-sounding basses and pretty much anything you can do with a subtractive synth, but to avoid going too much into making this just about FM8, I’ll leave it here.

If you want to learn more about FM8, check out friend-of-the-family Tim Cant’s video for Native Instruments:

If you want to check out some other FM8 patches I’ve done have a read of this tutorial on ambient pads or this on Aphex Twin’s Xtal or this on Squarepusher’s Tommib, all of which include downloads.

Arturia Synclavier V

The New England Digital Synclavier is somewhat of an enigma – everyone has heard of it (and heard it on various records) but few have used one, let alone seen one in real life.

Produced between about 1977 and 1980, similarly to its British cousin the Fairlight CMI, this combined the new technologies of sampling with additive synthesis and frequency modulation.

Not only would you have had to part with around $200,000 (far more by today’s rate accounting for inflation) but these were notoriously tricky to program.

Luckily for us, the good guys at Arturia have made a software version, retailing at a very reasonable €199 at the time on publishing.

Patches in the Synclavier are referred to as Timbres. Timbres can be made up to twelve component partials, which you can think of a little like oscillators. The original Synclavier only had four partials so the Arturia one is three times more powerful.

There are two windows for the Synclavier, the first is the timbre edit page (here, highlighted with a green box). Here we can make broad changes to all of our partials, changing their amplitude and FM envelopes, FM amount as well as voice information and we have a basic arpeggiator.

By clicking the button (white arrow) at the top we can expand the timbre edit page (white box). This allows careful and detailed control of each of our twelve partials including their pan position, tuning, FM amount, frame speed (more on this later), envelopes for amplitude and FM and two LFOs, one for pitch modulation and panning. Partials can be copied and pasted as well as solo’d and muted.

By click the SCR screen page we can access a more visual edit page for our partials. There are tabs (pinky/red) for each of the twelve partials amplitude and FM envelopes (which they refer to as harmonic envelopes). The envelopes are as to be expected, with time values for delay, attack, decay and release as well as peak and sustain portions. Partials can be shift-selected allowing for batch editing.

We also have a tab for assigning partials to key zones, a time slices page (detailed below), a basic mixer, MIDI modulation matrix, FX and global settings.

The time slices tab is where most of the engine room of this synth is. We have carrier and modulator operators each with control of of the amplitude and phase of up-to twenty-four harmonics(!). There are various edit controls such as templated geometric waves (sine, saw, pulse, triangle), drawing tools (pencil, eraser, straight line etc) and “coefficients restrictions”, which is nothing to do with the UEFA Champions League as far as I can tell. This means we can restrict the harmonics we’re selecting from ‘all’ to odd numbered, even numbered, octaves and fifths.

The sheer scope of potential sounds available here is huge – sitting somewhere between the simple yet powerful design of Ableton’s Operator and something more complex but slightly scary like Native Instruments Absynth.

Where it really comes into its own as  a proper additive synth is the frames themselves. These are states that can be morphed between a little like the wavetable index of Serum or Massive. I’ve not found a limit to the number of frames you can have. Here just one partial with no frequency modulation – morphing between the basic partial and seven additional frames, each with a different harmonic makeup.

Really the best place to start with for learning the Synclavier is Arturia’s own sound design videos on their (excellent) YouTube channel. I’ve embedded part 2 of their look at the Synclavier as a lot of the content in part 1 is covered by me (albeit in slightly less detail) above. This goes deeper into what can be achieved combining the various synthesis engines in the Synclavier. Enjoy.

…and Finally

I wanted to finish off with an excellent Mylar Melodies video. This is a video about the ALM Akemie’s Castle eurorack module – crazy 4 operator FM synth fully CV-able. What’s really interesting about it is that it focuses in on the sounds capable of (for want of a better phrase) messing around with FM.

Something mylar melodies mentions is that while we all know and understand subtractive, there’s a sort of unknown quality about FM that still makes it interesting and possible to stumble across bizarre sounds.

The linear nature of the signal flow in a subtractive synth means that although we could all improve our understanding a little, it’s rare you’ll surprise yourself. FM on the other hand has oscillators interacting with each other at its core level, and the fragile nature of their interaction is fundamental to the scope of sounds that FM can produce.

I hope you’ve enjoyed this tutorial and have hopefully learnt something new; I had a lot of fun researching it. It’s actually been in my drafts for ages but I’ve been refining and tweaking it to ensure I do sufficient justice to the topic.

If there’s something I’ve missed out it might either be accidental (I am human) or deliberate (perhaps it’s too technical for these pages) – either way, please do let me know in the comments or get in contact. Have fun!