Algorithms and their effects

I’m new to Digitone and FM synthesis in general.

I was wondering if some of you with more experience could tell me: Do the 8 different algorithms have a particular ‘character’, or is it more about what you do with them?

Like I said I’ve very new and still toying with the params, really.

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IMHO some readings about FM synthesis are necessary.
Take your time to learn this and experiment until you understand it.

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I think it’s best to think of the algos as having 4 basic shapes:

  1. Stack - (eg algo 4) with this configuration the modulation of each operator is gated by the operator below it. So the effects of B2 is only heard when modulation B1, which is only heard when it effects A, which is only heard when you modulate C.

  2. Branch - (eg algo 1) with this configuration multiple sources modulate the same operator. So B1 can still modulate C even if A’s modulation depth is turned all the way down.

  3. Root - (eg algo 3) with this configuration the same source modulated many operators simultaneously. A modulating C, B1, and B2 at the same time allows for a stacking of timbres in addition to modulation.

  4. Carrier only - (eg algo 8) with this configuration the operator is directly part of the mix with no source modulating it. The digitone doesn’t have a great example of this but algo 8 comes the closest. Perhaps the easiest use case for such an algorithm would be to make an organ sound or mixing some fundamental back into a crazy sound.

All algos on any FM synth are combinations of these parts. So I tend to choose my algorithm based on whether I need to nest the modulations in a stack, have them mix together in a branch, or have sounds layer with a root.


Thanks. I do find #4 the easiest to understand. I just wondered if there was a deliberate choice for why the others are routed how they are - if they represent something, or if they’re suited to particular sounds. I guess it’s more about having the X-Y split behave in different ways?

That’s more of a question for @Ess as which algos a synth provides are the choice of the designer. I would imagine the considerations were:

  1. can it be parameter locked to another algo and have it still produce sound?
  2. is it different enough from the other algos to justify?
  3. is it versatile within itself to create a variety of sounds?

edit: I found what @ess had to say on the topic

I too would like to know if there is a style of patch that was anticipated for the algorithms. Some of them are pretty unique (algo 6) and wonder if they are inventions or inspired by some synthI never heard of.


There is definitely an intention, why the algorithms are so different. I try to explain this on some general examples.

  1. All operators are parallel:
    Well there is no FM obviously, but we can have for each operator a single waveform at a different pitch, which would be like having a very simple additive method. Organ like sounds can easily be done with such an algorithm.

  2. All operators are in a single chain:
    This gives us much FM. Only one operator generates sound, all others are modulators for modulation of the next level.

  3. All operators are building pairs of two:
    Each pair is a complete FM voice in its own right and can have a sound and pitch, which is totally different from the others. We could use this to combine the different sound characteristics for different tasks, like a sound for the transient phase, a sound for the sustain phase, a background sound and others. We also could use those independent sounds to layer the 2-operator sounds.

Well, all other and more complex algorithms take us to much more complex options.


This is a good explanation. Its why algorithm 4 can be a wild beast to tame. Personally I would love to see an expansion of algorithms on the digitone.

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I have to admit, I’m FM dumb as far as this algorithm talk goes. I think Elektron made the Digitone easy to come up with very musical results for dummies like me. It would be nice to get an overall explanation into the algos, maybe an analysis of sorts. Perhaps start reverse engineering the preset patches.


My approach is purely experimental. I have a basic understanding of FM synthesis, the algorithm types, and the architecture of the Digitone. Other than that, I just twiddle the knobs until I find a sound I like.

Previously I was using abletons Operator, with its infuriating UI. Digitone is so much more playable, user friendly and fun, plus Digitone has that xy mix knob, which is genius! Two patches is one!

I think the algorithms do have their own character, or perhaps a better word is behaviour .Understand how the algorithm behaves, and you have a head start on your decision making.


+1 for Knob Twiddlin’ , which is also my go to operation with the DN.


If you understand, what can be done with a pair of FM operators, I would say that you have already understood the most important part.

Even a pair of operators can create an overwhelming number of very different sounds. Most of those patches are very sensitive to small variations of the modulation and with a well thought-out modulation of pitch and timbre such a pair can sound like two or more different instruments playing together … not layered, of course.

Algorithms are making things only more complex and give us more options.

My approach to understand algorithms is to search for clusters, which make sense to me. This would be pairs, triplets, chains of two, chains of three, how many independent clusters I have, if there are any links between clusters, which I would like to use or not. Often I use the clusters as single voices, or ignore them at all.

We should consider that if even a pair of operators can generate very complex sounds, it is not making much sense to combine as many operators as possible in a chain. From my experience I can tell that a third operator added to a pair of operators can be very good used to add some grit or an other variation to the patch, but often enough only, if applied in very small dose.

My personal rules of thumb are:

  • even two operators generate very complex sounds using very simple waveforms like sine or triangle
  • a third instance of modulators creates even more complexity
  • the more complexity we add, the more we enter the territory of chaos or noise

It’s worth keeping in mind that the envelopes play a very sensible role in how the algorithm shapes the sound. It basically modulates the activation of each oscillator.
Chowning defines an operator is the set of oscillator + envelopes, btw.

Especially watch out Env B that has a very specific behavior to give the amount of activation of B1 and B2 with only one



Do you have any ressources to suggest?

these are good fm tutorials. Can‘t remember how much they talk about algorithms but they explain the carrier-modulator interaction. In the algorithms you have to make clear which operators are carriers, which are modulators.
But I agree with @SoundRider. More than three operators can get very complex. I make many sounds with only two. Envelopes of each operator have big impact.

On the digitone simple knob twiddling even with all 4 operators lead to many happy accidents since it‘s designed mainly as s sweetspot fm synth :slightly_smiling_face:

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Imho FM8 is great for learning fm synthesis, because it lets you freely connect operators, set up operator feedback and turn operators off/on with right-click.
Also there‘s an overview of all envelopes, so it’s easy to explore which operator connection does what, how modulation amount, feedback and evelopes influence the sound.
Full control over the fm without getting lost in a parameter jungle.

FM8 can import dx7 and a other (IIRC
DX11/TX81Z, not sure about others) sysex patches.
Factory libraries from Yamaha FM synths and tons of other patches can be found on the internet.

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really great synth

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The video at the bottom is one of the most “fun” explanation of FM synthesis I’ve had the joy of watching. The title is misleading but it’s an explanation of basic FM synthesis and how it works (modulator carrier and harmonics). The algorithm he uses is is basically the same as Algorithm 4 on the Digitone.

Different waveforms can be chosen or “made” by changing the “harm” (harmonics) knob on the Digitone. Once you understand that the modulator modulates the carrier, you’ll see that the algorithms just give you more ways to be creative with routing modulators to carriers for sound design. Add the Elektron advantage of P-locks and an enormous world of changing evolving sounds opens up.

A relatable example: A LP filter on an analog synth removes higher harmonics when you sweep the filter down. You can do the exact same thing by reducing the volume of the a modulator going into a carrier on an fm synth without using a filter to do so. FM is more of a “direct” manipulation of the harmonics instead of set waveforms and filters you make waveforms and manipulate their harmonics.

The algorithms provided in the Digitone just try to give you the most possible preset routing options you can do with the 4 operators. I doubt there is any specific “make this type of sound” reasoning behind the algorithms. It’s simply these algorithms cover most of the possibilities of routing 4 operators that they can come up with and that seem useful.

I love it so much that I have a regular Digitone and a keys now :slight_smile:

It’s based on operator but the underlying concept is the same. Dick is short for Richard BTW, enjoy!

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Tao of FM synthesis and above “inside synthesis” video were really eye-openers for me.