Modular synthesis in Reason part 1: Creating a basic monosynth

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When you think of modular synthesizers you might envision a huge Eurorack system complete with countless dangling spaghetti cables. It’s the king of hardware gear, the holy grail of synthesis that’s reserved for the few enthusiasts that have spent countless hours and a vast amount of money perfecting their dream instrument. It can quickly turn into an addiction that can completely take over your life. Ok, maybe I’m over-exaggerating a little bit here, but it’s not hard to see why modular synthesizers are so desirable.

However, you don’t have to spend a tonne of money to build your dream modular synth. You don’t even have to a clear a room out to house your massive Eurorack system, not when you have the power Reason at your disposal. Don’t believe me? Just flip the rack around in Reason, don’t those spaghetti cables look familiar?

Sure, using software to create your perfect instrument isn’t as glamorous as owning the real thing. You won’t get the satisfaction of hand patching the cables or turning the physical knobs but you will get to explore the world of modular synthesis for a fraction of the price.

Just check the Propellerhead shop and you’ll find loads of Rack Extensions that will help you on your way to modular madness. With all this choice it might not be clear where to start so I’m going to be writing a series of tutorials here on RER to get you up and running.

In this first tutorial I’m going to be showing you how to set up a basic monosynth using modular synthesis within the Reason rack. To follow along you’ll need Ammo 100LA (€15) and Charlotte Envelope Generator (€19). Let’s get started, if you get stuck be sure to check out the example images provided.


  1. We’ll start off by creating a combinator, in that combinator create a 6:2 Line Mixer. You can use the 14:2 mixer if you want but to save space we’ll stick with the 6:2 for now.

Line Mixer 6:2 inside the blank Combinator.


  1. Next we want to create an instance of Ammo 100LA and an instance of Charlotte (hold down shift when creating it so that Charlotte doesn’t auto-route to Ammo).
Don't Forget to hold shift when creating Charlotte.

Don’t Forget to hold shift when creating Charlotte.


  1. Before we go any further we want to make sure that Charlotte can receive midi messages. Click the ‘show programmer’ button on the combinator, then select Charlotte from the list on the left and check the box that says ‘Receive Notes’.

When you’ve checked the ‘Receve Notes’ box, feel free to hide the programmer again.


  1. Now let’s get some sound out of Ammo, flip the rack around and connect Ammo’s audio out 1 to channel 1 on the mixer.

No sound yet, lets move on and set the oscillator range.


  1. Flip back to the front and you’ll notice that Ammo is sending audio to the mixer but you can’t hear it, this is because Ammo is in ‘Low Rate’ mode (its’s producing audio below human hearing). Click no the range button on Ammo twice so that it’s in ‘Semitone’ mode.
Feel free to turn down your speakers until the next part is completed. The droning can quickly get annoying.

Feel free to turn down your speakers until the next part is completed. The droning can quickly get annoying.


  1. You should now be able to hear audio from Ammo, but at the moment it’s just a constant drone. We need to hook up Charlotte’s envelope so that we can use it to control the amplitude and pitch of Ammo (this bit might cause some confusion, but if you get stuck refer to the example image below) —Flip the rack around and connect the ‘EG’ CV from voice 1 in Charlottes ‘VEGN Group Outs’ section to the ‘Env’ input in Ammo’s ‘SEQUENCER’ section (This should stop that constant droning). Now connect the the ‘Gate’ and ‘Note’ from Charlotte to the ‘Gate’ and ‘CV’ on Ammo, just like you did with the ‘EG’ CV.
Ammo and Charlotte are the perfect pair.

Ammo and Charlotte are the perfect pair.


  1. Now everything’s hooked up at the back of the rack we need to set up the envelope in Charlotte. Flip back to the front and take a look at the Charlotte’s envelope section. Set the ‘Level’ of stage 1 to 100 and the Time of stage 9 to 1ms.

Now we’re getting somewhere.


  1. Ammo should respond to the keys on you midi keyboard but it’s still only playing one pitch no matter which note you play. This can be sorted by setting the ‘Kbd/Porta’ knob to on.
That's it, everything's set up now.

That’s it, everything’s set up now.


  1. You now have a basic monosynth that plays a basic sine wave. Sine waves are a bit boring so let’s change the waveform on Ammo to a sawtooth wave (003).
Sine waves are boring so we're going to change it to a saw.  Ammo 100LA has 128 waveforms so there's plenty to choose from

Sine waves are boring so we’re going to change it to a saw. Ammo 100LA has 128 waveforms so there’s plenty to choose from.


What we’ve created throughout this tutorial is a basic monosynth that can be used for the basis of loads of cool patches. It’s a bit boring at the moment but in the next few tutorials we will build upon it to create a nice lead patch that will feel right at home in your productions.

Notable mentions:

–    A-Series 1 & 2 (€7.50 each) – A must have for any modular synth enthusiast. These we’re designed exactly for this purpose. Buying both devices gives you a pretty impressive set of modules to get you started: MIDI to CV, 4 wave VCO, envelope, VCA, 4 wave LFO, poly splitter, sample & hold, noise generator, VCF (high pass and low pass), ring modulator and a mixer. That’s a lot for such a small price tag.

–    Pulsar (€39) – One of Propellerhead’s own, Pulsar gives you two LFOs as well as a built in envelope follower. The LFOs go all the way up to audio rate so you can also use it as a fully fledged monosynth.

–    CV Suite Line Processor (free) – CV plays a huge role in modular synthesis and this device let’s you take control of them. If you want to warp, tweak or completely change your CV signals then this free rack extension is for you.

–    Scope Jr (free) – Another freebie from the Propellerhead shop, this time in the form of a basic oscilloscope. The display is a bit primitive but Scope Jr will let you see what you’re signals (both CV and audio) are doing.

–    Lolth (€7.50) – Lolth will do more than just split your CV signals, it will also let you delay the splits and tempo sync them. I find this useful to create a strumming effect, similar to that of a guitar.

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Freelancer and sound designer from the UK. Interested in all things music tech.