Subtractive Synthesis 103 – Modulation and what is an LFO?

Following from the first two post in the series (Part 1 and Part 2) we are going to learn how to turn your synthesizer sounds into fire breathing animals from the future.

So what is Modulation?

So far we’ve used a basic subtractive synthesis to construct a static tone. Which is pretty cool but we want is something AMAZING. This is where modulation comes in. Modulation just means to change. You’ll hear this term anyway from people talking about production, labeled on effect boxes (i.e chorus rate) and more traditional music scoring. Modulating through key changes.

How is it Useful?

Music is time based medium so the tricky part in writing is developing ideas that not only work in three dimension but also hold interest over time. Modulation of synthesis parameters is one of the classic production elements for you can add to your creative tool kit.

Explore Modulation Routing.

Using what we built on in this post on Signal Flow  we know that you can push signal around in anyway you can think of. A flexible synthesis will allow you to do this take one part of synthesis and using it to modulate or manipulate it.

Something like this:


Common Examples:

LFO – Low Frequency Oscillator. One first this that gets used and abused when you start out learning production. Your first track will be riddled when LFO like the new dj who put flanger over everything track.

The low frequency part comes from the rate cycles. Unlike human hearing the LOW FREQ will set below 20 cycles which means that we can’t hear but we can abuse it. By routing the LFO into different parameters we can “modulate” it the same way as if we turn the knob in real time.

Depending on the wave form shape triangle, square, sine etc will determine the way it’s going to modulate.

Straight Sine LFO modulating pitch

Square LFO modulating pitch:

Try this, take our TAl ELECTR7 and using lfo number one set the sine wave, amount full and route it to pan. Now slowly increase the rate and listen to the shift between the speakers, now switch to square and notice how it “jumps”.

Pan Mod Examples.

Square Wave LFO:

Modulate both Pan and Pitch with a Sine wave:

Flexible Routing Systems:

Now that we have the basic idea. We can build on it further with the use of multiple filters or routing different control amounts to different parameters (Pan, Pitch, Volume, ADSR curve, Effect Sends etc). The sky is the limit here.

(If you need a freeware alternative check out this site for some great ones

What if start using two LFOs for modulation of different parameters.

Two Lfo Controlling The Different Parameter At Different Rates:

Two LFO Controlling The Same Parameter At Different Rates:

Try two LFO modulating each other control rate:

Experiment with these and record the stuff you like. Sequence into a musical phrase and BOOM!!!

Share, Subscribe and Stay tuned because in the next post we are going to look at Classic Compression Uses and Abuses:


Enjoying Little Dragon at the moment:

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History of the 303…

Fantastic little documentary about 303 and it’s impact on modern culture.

Stay tuned, Share and Subscribe


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Subtractive Synthesis 102 – Filter and ADSR

Welcome back…for those of you who don’t know, this is part 2 of our intro into subtractive synthesis. If you missed the beginning go here now.

In the last post, we covered a little about subtractive synthesis and we started to explore the idea of how tone generation works. This week we are gong to take the tone we made in part 1 and shape it further….


Filters are the third part of the equation of basic tone construction, the other two being wave-tables and volume envelopes. This is one of the most fun parts of synthesis. There is also an added bonus of being able to transfer this knowledge elsewhere in the audio production environment.

So what do they do?

They filter out a signal so you can’t hear it.

Core components of the filter:

DB per octave (roll off rate): This is the steepness of the curve. The steeper the curve the larger the number. The higher the roll off rate, the sharper the filter. So a 6db per octave would reduce the signal by 6db every musical octave where as a 24db per octave filter would reduce the signal by 24db every musical octave

How steep you make the roll off rate will depend on what you are trying to achieve but a basic rule of thumb is:

The steeper the curve the more unnatural it will sound.

Next,  the filter knob is another knob which you might not know but will have definitely heard of. The ‘Resonance’ controls the filter point volume. Crank it up and watch the filter point get really loud using this.

Classic Acid House.

The four horseman of the filter:

LP (Low Pass):
The ‘Low Pass’ allows only sounds below the filter point to be heard.

HP (High Pass):

The ‘High Pass’ allow only sounds above the filter point be to heard.

BP (Band Pass)

‘BP’ is a combination of the LP and HP.  This allows only the sounds in between the two filters to be heard.

LP + HP = BP

Notch (Band-Reject)

The ‘Notch’ is the opposite of the band pass. It allows only the sounds outside of the area to be heard.

Invert the BP…

Get your hands dirty:

Load up your project with your 1 bar loop.

Add a band pass filter

Just move around til you find something cool

Take your volume fade, click 4 nodes. These will be our ADSR envelope.

Place them like so.

Use additional nodes to adjust to taste

Adding bit crusher changes the 2nd sound just touch. So it feel more human

Finally add a reverb because we can.

No rule just play, You can use the volume curve on your channel to edit decay if you’ve gone for a long decay time.

Awesome, you have just created your first sound.

From here you can render it out and we can move it into the sampler.

“What about the filter ADSR curve?”

ADSR envelope can be applied to the filtered section as well. Instead of the sound being shaped over time, the filter movement will be shaped instead.

I’m going to let you experiment here.

Move back to the synth, initialize it and move through the steps: tone, filter then ADSR and create another patch.

IDEAS: Things to try out: make an identical to the volume ADSR,  an opposite and an inverted. Then go for your life.

That’s it for this week, stay tuned next we are going to place our sound in our sampler and creating a unique instrument.

As always subscribe and share.


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Tone generation and Subtractive Synthesis 101

Last post we cover the ADSR envelope here. I know this concept is a little difficult to get your head around but stick with it. The pay off is completely worth it.

What you’ll need for today:

1 ) A Synth plug-in. Today I’ll be using TAL Elek7ro – Mainly because it’s free, non DAW specific and you can download it here.

2) Spectrum analyzer: If you don’t have one, grab this.

So what is Synthesis?

Fundamentally all sound sources can be broken down into a mathematical relationship of tones. How these tone can be created, expressed and interact is some seriously high level math. As in…a basic saw wave looks like this…

y = A - \frac{A}{\pi} \phi

Input: Peak amplitude (A), Frequency (f)
Output: Amplitude value (y)

y = A - (A / pi * phase)

phase = phase + ((2 * pi * f) / samplerate)if phase > (2 * pi) then
      phase = phase - (2 * pi)

Looking that over, I smell fear in some of you right now but don’t stress there is no math involved today.

What you need to know?

All sounds have two main components, they are:

Fundamental – This is the lowest pitch of the sound and forms the start point from which the partials emerge. The main function of the fundamental is to provide the pitch information. C C# etc.

Partials/Harmonics/Overtones – different form of sonic information. All sounds will  have combination of these and this combination is what provides the instrument’s characteristic information or timbre. It’s this part that lets you tell a shaker from a bell even if the pitch (fundamental) is identical.


This knowledge is amazing useful if you’re interested in re-creating or creating new sounds and textures. Understanding the function of the fundamentals/harmonics and the way they interact should give you a head start in implementing desired timbrel quality into your own sounds.

So many different types of Synthesis, I don’t really understand the difference?

The basic idea of all synthesis is pretty much the same, the route they use to get is a little different and as such they all have there own unique qualities that are useful in different circumstances.

Follow these links for a deeper overview about the various different types of synthesis: subtractive synthesis, additive synthesis, wavetable synthesis, frequency modulation synthesis, phase distortion synthesis, physical modeling synthesis and sample-based synthesis )

But today, we are going to look at subtractive. It’s the simplest to grasp in terms of design, common in all styles of music and is a great way to understand the fundamentals that we are going to build on later with other types of synthesis.

What is Subtractive?

In a Nutshell: You build a complex tone using simple wave shapes, then by using a combination of filters and manipulation of the ADSR curve you reduce or “subtract” it into it’s final sound.

Let’s look at the various basic wave forms and build on from there.

Basic Wave Forms:

Sine – Pure fundamental, no additional harmonic information.

Pulse wave- is rectangle in shape and depending on the pulse width (normally labeled PW) can contain a range of both even and odd harmonics. Setting the pulse width somewhere in the 50% region will turn it into into a square wave. Some synthesizers will have a Square setting, some will have a Pulse and a Pulse width.

Saw – Contain both even and odd number harmonic information.

Triangle – Contains mainly odd harmonic information, similar to the pulse wave except due to it mathematics equation it uses the high harmonic content will roll off alot faster.

Noise- Just that random harmonics. Useful but not exactly musical.

Even and odd order harmonics is a whole other topic that I’ll cover at a later date. But a sound with more even harmonics is warm and musical. More odd order harmonics is harsh and biting.

Getting our hands dirty:

What we’re going to do today is create our own tone and using your DAW we’ll mimic what is happening inside the synth. This is a great way to visually process each step and slows the whole process down.

Okay, so open up your DAW and place the TAL then a spectrum analyzer on the channel strip. It should look like this.

Something like this… Make sure turn down your OSC 3 which defaults on.

Create C3 midi note and hit play.

In this section. Click Sine. Now look the analyzer. See how you got one pure tone or your fundamental.

Push the Sine. Use the Semi tone knob to ensure the pitch match the note being played


Yeah, Pure tone

Well… not quite

Now you’ll notice here that there is additional overtones occur. Not a pure sine wave but close.

Click the triangle and look at the way the upper harmonic content filters off rather than on the pulse or saw.

Below the fundamental you’ll see what is refer to as a sub-harmonic.

Click through the other basic waves. Take note of the way the sound changes with each wave.

Making Our Own:

Now let create our own custom harmonically rich sound. Drop the Tal Bitcrusher or any sort of distortion (harmonic generating) plug in on it. Play around with parameters and keep your eyes on the spectrum analyzer. Watch the way the additional harmonics shape and change the wave form.

Find a cool tone and then render the sample as a 1 bar audio loop.

We have now just created a tone ready to be shaped.

Tune in next post as we going to continue on and use both filtering and the ADSR envelope to shape the sound further.



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Back next week.

Haven’t forgotten. I’ve just started a brand new project so it’s derailed me a little. Should be back on track for next Monday. till then enjoy.

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