Creating External FM in Reason

FM Synthesis isn’t the easiest thing to get your head around and while it can be full of wonders much of what you will do will create a ghastly scraping noise even Satan would find distressing.

Mostly FM Synthesis will be created using simple tones inside the same unit, think Yamaha DX 7 or Casio CZ-1000 (yep that is more FM than anything as different as marketing would lead you to believe) however you can use several synths or even LFOs to create FM. This method will be a lot rougher but also capable of some way out results.

Here I will show you using a Malstrom and Thor in a Combinator in Propellerhead Reason. This is technically possible in any host that allows a reasonable amount of modularity but this is somewhere Reason excels.

Let’s get started:

  1. create a Combinator (a box or folder to hold the units and get them to behave as a single unit)
  2. then insert a Malstom
  3. now insert a Thor and set the Filter to Bypass (maybe turn the volume down a bit too)
  4. swap the Thor OSC to an FM Pair OSC and set the FM amount to 0
Malstrom+ Thor FM Front
Malstrom+ Thor FM Front

We should now have two synths with Sine waves that start their duty cycles at the same place with each note on. This may seem a small point but later you will find it helps get more consistent sounds with successive key presses.

Flip the Rack and:

  1. unplug all the internal wiring
  2. cable Malstom Main Out Left to Thor Audio In 1
  3. cable Thor Main Outs to the Combinator Outputs
  4. flip the rack back
Malstrom FM Back
Malstrom FM Back

You now have a simple Sine wave coming from Thor with no modulation. Let’s get interesting:

  1. in the Modulation Matrix choose Audio In 1 as a Source and OSC 1 FM as the Destination
  2. play some notes and slowly raise the Mod Amount

You will note that the higher the Mod amount the gnarlier the sound becomes. This is FM, modulation of one oscillator by the output of another.

As long as you play one note at a time the sound is relatively stable but once you get your Poly on (play several notes at once) the sound will suddenly get really ugly. This is because when using several instruments to create FM you are using the total output of one instrument to modify another. One sine wave is simple but two at different pitches is immediately complex.

If you have Reason you can start to assign some parameters to Combi Knobs to create a more playable instrument. Anyone who has read this far is now dying to try using more complex waves than boring old Sine waves. The world seems to open up as you can assign samples of your Mother In Law in full flow to modulate your cat barfing.

If you have Reason 6.5 here is the FM Patch

Have fun.


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