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Make a modular synth in Reason

Published: 2017-09-04

Thor can be used as an effect unit, while at the same time this device can be a fundamental building block in to creating a true Modular synthesizer. The only thing we need to understand is how a modular synthesizer is build, how it works and how we can create one from the ground up again to make something custom and unique at the same time. Yep, it is Monday and today it is time to geek out with Propellerhead Reason!

It is all happening in the back of the Rack

Before we get started with this topic, I would like to address that this tutorial about Propellerhead Reason may require some understanding on how audio cables and Control Voltage cables work. We have covered basically a lot on those angles. So in case you still haven't figured those parts out yet. Let me give you a two part video about the basics on routing cables.

Once you start to play around with these type of connection you will truly unlock the powers on what Reason can do. On a personal note, you do not have to use them at all to create sounds. If these type of things are not your cup of tea, then no worries. But this subject might just be the subject for you either.

What is modular synthesis?

Modular synthesis in real life

To answer the basic question on what modular synthesis is, the basic answer is that modular synthesis is a system where all the individual segments of a synthesizer are all loose end blocks or modules. While a synthesizer that is as a final product usually contains all those elements as build in elements. These elements would usually be presented as followed:

  • One or More Oscillators
  • A Filter
  • An Amplifier
  • An envelope (to control either the oscillator, the filter or the amplifier)
  • A Low Frequency oscillator
  • Effects

The path of the sound may vary on the way how a synthesizer is programmed. The most linear direction would be:

  • Oscillator goes through a filter
  • a filter goes through the amplifier
  • one envelope is used to control the filter
  • one envelope is used to control the amplitude

Most often we have an additional envelope that is used to trigger something else. For instance if you look at the Subtractor (stock device in Propellerhead Reason) it contains a section for modulation envelope. This envelope is often used to trigger 'specific' needs depending on the capabilities which the synthesizer has. With in the Subtractor these are Phase, Pitch, Frequency modulation and mix settings. Since these are the unique trigger points on the Subtractor in that specific case.

Modular synthesis explained

Part of the beauty of a modular synthesizer, it all depends on how you build it, how the structure is and you can define yourself how complicated you want it to be. Always keep in mind there are different ways to modulate things, there are different key controls (midi) that can (or may) have an influence on the sound itself. Just decide for your self which element you need when trying to build a complete modular synth from start to finish. It does not require everything I am going to address inside this tutorial. Just to make it easier I am going to go for the linear approach on how to set up a modular synthesizer. While this path can be broken, re-arranged and so on. But by reading along with this, you may grasp more on what is really happening with modular synthesizers.

The Oscillator in a modular synthesizer

The heart of the system is driven by the heart of the synthesizer itself: the oscillator. The oscillator will define the sound. While traditional analog modular synthesizer usually contain one of the following wave forms:

  • Sine
  • Triangle
  • Square (in the form of pulse width)
  • Saw
  • Noise

A lot of the modular synths use either one of them (or you can pick from them). While if you look at Thor itself, there is an oscillator that already contains for of the above. The analog oscillator is indeed the idea candidate for setting up the initial oscillator. At some extend you could use two oscillators where one is the wave form from the analog oscillator while a second oscillator will be the noise oscillator. That is also partially the beauty behind modular synthesizers is that there is usually no linear solution to any given synthesizer. Every build can be different.

Modular synthesis in Reason using analog oscillator

So in this particular build I will go for 2 different Thor patches that contain one oscillator per Thor. The first is going to be the Square tone (just because of Pulse Width I find this an ideal combination). The second Thor patch will be a single noise oscillator. I am using different Thor instances just to embrace the modular setup. In theory you could use two oscillators in one Thor. 

The idea behind oscillators in a Modular synthesizer is that once these things are 'added' the sound will play an endless sound (never ending loop). The only thing the oscillator will listen to is the pitch variation once a different Note Event is triggered. In theory this can be accomplished with Rack Extensions like A-Series from OchenK or the VCO (viking oscillator) from Blamsoft. While using Thor this might become a bit problematic. But before getting in to this, there is just the minor issue referred as polyphony and a monophonic synthesizer.

Polyphonic vs Monophonic

Before continuing about Oscillator there is one important note to make. With most modular synthesizer (think: euro rack designs) the core sounds are most often monophonic. The main idea with a lot of these big rack synths is that they are driven by an Analog Sequencer. So if you translate this towards Reason: you have a subtractor and this is being triggered by a matrix pattern step sequencer. While re-designing a complete modular synthesizer we can of course you can bend the rules a bit and still turn a monophonic synth in to a polyphonic synthesizer. For this course in particular we will mainly look at the way for creating a monophonic version. Polyphonic synths in terms of modular are harder to build (there are 'quick' solutions for this though).

Now that we quickly addressed the issue with Polyphony we'll be using an instance of Thor which will have a monophonic sound. 

  • The Polyphony count will be set to 1
  • The release polyphony will be set to 1
  • Optional would be using mono-legato (this automatically means that only the polyphony count will be set to 1)

Modular synthesis using Thor

Display on the polyphony settings for using a monophonic output

Endless oscillator using Thor

By default (if you reset Thor that is) the oscillator 1 will go trough filter 1 then through the Amplitude and then it goes through filter 3. In this case we do not want to do this just because of the idea that we want to have an endless audio from the oscillator without any envelopes to this attached yet. The Oscillator will need to go from Oscillator to Audio Output 1 and Audio Output 2 (left and right).

Modular synthesis in Reason using Thor. Setting up the oscillator

To program this inside Thor we could do the following:

Source : Oscillator 1 > Amount : 100 > Destination : Audio Out 1
Source : Oscillator 1 > Amount : 100 > Destination : Audio Out 2

The cool thing however is that you can also change this chain by for instance using Oscillator 1 to go through left and Oscillator 2 to go through right. If you really think in terms of a modular synth then I would use two different Thor patches (one for left and the other for right).

In this case every time you hit a note you will hear the oscillator change the pitch but at the same time it will be a constant tone (and it never stops... in theory).

The Gate in modular synthesis

While in normal synthesizers the gate is being triggered when ever we press a note or key. In terms of Modular synthesis the gate is usually generated by a pulse generator (clock). At the same time we can do some creative gate generating when it comes to reason. Since we can either determine to set up a gate that gets generated by pressing keys (midi key > gate). Or we could decide to use an LFO, external curve from a matrix pattern step sequencer. Etc. As long as there is something that goes on / off. Because a gate is nothing more then turning things on and off.

Programming the gate in modular synthesis

To program the straight forward gate while listening in to the the midi keyboard, we could set up an instance of Thor to do the following:

Source : Midi Gate > Amount : 100 > Destination : CV Output 1

One thing we could do next is to connect the CV output to the CV input of the oscillator Thor patch so in that case we can use the gates to turn on / off the audio through.

Modular synthesis gate processing

In this case the gate output is passed on from one thor patch to the other thor patch. The argument might be that the Oscillator Thor will have the exact same thing of course. The only reason why I am presenting it like this is because the Gate could be anything that sends out gates.

To program the receiving end, we can scale the audio source as followed

Modular synthesis gate processing receiver

As you can see over here is that the audio through put gets scaled in this case by the Control voltage input. Which in theory is in this case the midi key gate (since this is programmed in side the gate Thor patch). So if we press and hold the note, the sound plays. If we release it, the sound dies. Kind of like someone is opening / closing the volume on a press of a key.

Step sequencers in theory are build on this idea. Since they send out pulses depending on the position of the step sequencer and what value it has been set too. So in theory if you would replace the Gate output from the Thor with, lets say, an Analog 16 Step sequencer the gate output of the step sequencer will turn the Thor patch on and off. Make note, it does not alter the pitch (since this is still handled by the midi keyboard / on screen keyboard).

modular-synthesis-initial-combinator.cmb

Gate to translate the Envelope

Next thing we can do is translate the gate towards an envelope generator. To do this we'll do the most straight forward approach to handle this. Because in theory the gate gets triggered and when the gate gets triggered the envelope gets triggered. The only thing that will be different in this case is that the envelope will result in to a Control Voltage and we can then use the control voltage to control the output level.

The envelope generator could be looking like the following:

Modular Synthesis envelope generator

In this case only the Amp Envelope section is being used. While in theory this envelope could be replaced by any envelope generator. It only needs an attack, decays, sustain or release. So in this case even the Global Envelope (set to loop mode) could be used as an envelope generator. There are rack extensions that do such a thing pretty well. For instance Blamsoft has a envelope generator for their Polymodular Systems. Also Charlotte by Jiggery pokery is an awesome envelope generator to mess around with. There are plenty of options to choose from. I am using the Amp Envelope just because it has "amp" in the name of this generator.

The Amp envelope gets converted to a control voltage output. So from this angle we can use the Control Voltage to scale the audio outputs.

Modular Synthesizer Envelope

In conslusion

In conclusion, reason is modular as it can be. While I personally think that most people do not tend to look at the rack in this context I felt like throwing in an article like this again just for the fun of it. It is a different take looking at how sound travels from one signal to another. You can process it further with filters, creative effects or modulate different effects with different cv generators and so on. The route can vary, the path can vary, CV can be manipulated,  you can stack as many filters as you like and so on. If you start looking at the Rack as LEGO then you unlock a whole different world.

This is Hydlide signing off for tonight. Have a nice evening.

Bye

 

Published on Reason Experts
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Published on Reason Experts
Published: 2017-09-04

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