Propellerhead Reason tutorials made by Hydlide

Published on Reason Experts

Essential LFO tricks in the subtractor part two

Published: 2017-07-03

Low Frequency Oscillators (LFO for short) are nifty little things to automatically modulate different settings inside a synthesizer. While these modulators are often being overlooked, in this article Hydlide will be diving more in depth about what powers lies ahead while using an LFO in Propellerhead Reason. They are present in most of the common synthesizers (like the subtractor, malstrom and Thor), here we will be looking mainly at the subtractor analog synthesizer. 

The LFO 2 in the subtractor

The LFO  2 is awkward little thing. If you compare this with lets say the first one the LFO 2 does not allow any method for syncing with the tempo. While at its best it has controls for setting up a delay amount and it comes with its own KBD switch. The last one is the most interesting one to play with, but more details about this in a bit. First lets look at what the LFO 2 has to offer.

LFO 2 in the subtractor

As you can see in the above picture, this typical LFO comes with settings for changing the pitch, phase, filter frequency 2 and the amp. Mostly modulating different type of characters which the first one has too. The default pattern is a triangle wave form. Yes, it does not have a sine wave pattern as a source. If you think about this for a second, it doesn't make much sense. But ok, we will just have to deal with it (since there is most likely no MK2 subtractor synth design being made). For what it is worth to say, it doesn't really matter much, since if you really need it, you could always use Thor the polysynth instead (I will most likely write a follow up article on this one)

So in a nutshell, the LFO is defined by the following:
- pattern: triangle
- destinations: oscillator 1 and oscillator 2 pitch, oscillator phase (subtractive and multiply), filter frequency 2 (!) and amplitude (=level)
- controls: rate, keyboard tracking per note (in short KBD), amount and delay

Tremolo LFO effect

Tremolo is an effect where in most cases the level gets adjusted defined by a pattern. While in theory using the sine pattern would be the ideal LFO pattern to use, with in the subtractor this gets replaced by a triangle wave. The nice thing however is that there is a delay switch available to us. Meaning we can play a straight note, and later on let the tremolo effect kick in. A basic step by step guide to set this up with be pretty straight forward (with most of the settings regarding the LFO 2 that is):

- create an instance of the subtractor
- select a wave form
- select Amp on the LFO destination
- set a rate (the higher it is set, the faster the amplitude changes will take place)
- set an amount (the higher the amount, the more the amplitude changes will have an effect)


When it comes to tremolo effects, normally you do not want them to sync up with the tempo. This is partially one of the reasons why using this LFO makes it an ideal candidate to use it. as a tremolo effect. If you really need a tempo synced tremolo effect. then I would suggest using the Malstrom or Thor in those cases (since they come with a tempo sync mode).

Phase difference per note

Subtractive Phase, or multiply should not be confused with phasing (audio cancelation). Subtractive phase is a method where the oscillator gets duplicated and the wave form subtracts itself. The phase offset determines the starting point of the wave form. Normally if you use a subtractive phase to a wave form you could manually modulate the phase offset by creating some form of "phase modulation" type of set up. The most interesting part while using phase modulation is using a different phase offset rate per note. This is where the LFO 2 comes in handy (with its KDB setting). The idea behind KBD and LFO means that the note height (pitch) will determine how fast the rate will be. The higher the note, the higher the pitch. The beauty behind these KBD settings is that they listen in per note (polyphonic!). Which means that in cases like these you can trigger different phase modulations while pressing and holding a straight chord.

Subtractor Phase LFO


This is a technique which was commonly applied through our Reactor Refill from 2015.

Pitch differences per note

When it comes to adding an additional 'analog' feel to things, the LFO 2 to pitch is most likely the way to go to. While this LFO can be connected to a pitch change per note, we can (if needed) also add an additional factor to the whole pitch change while doing so: LFO 1 set to waveform Drift. This adds an additional 'randomness' while creating a single instance of a Subtractor. Normally I would use these setups in combinators, where one setting gets changed from one to another with different amounts, different rates and so on. Because not only does this increase the voice count, but it also adds an additional random unison effect while doing so. Sure, it is time consuming to set it up, I will admit that. But once you get the hang of it, it is really worth it.

Alter pitch per note

The changes in the pitch are usually very subtle in cases like these. Think in terms like 6-ish or 7-ish. Everything that goes beyond the 10 becomes too much noticeable like someone is misplacing a tuning fork. And that is in cases like these, not the artifact you really want to go for.


Published on Reason Experts
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Published on Reason Experts
Published: 2017-07-03

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4 Jul 2017 


Excellent articles - thanks Hydlide. In this age of being surrounded by REs, and now VSTs, it's always humbling to be reminded how versatile the original instruments are when used by someone with a deep understanding of the basics.

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