Propellerhead Reason tutorials made by Hydlide

Published on Reason Experts

Creative LFO

Published: 2017-07-02

LFO, or Low Frequency Oscillator. If you have been using since day one, you will most likely have used an LFO once or twice. If you are new to Propellerhead Reason you may have used an LFO in the form of Pulsar. Yet never realized it was called an LFO. I am going to write down this article for a few reasons. First of all, I have had my beef with someone on the internet (a well known person who educates online). The whole discussion about this would be "pulsar" lfo and that this would be the best and only LFO to use in Reason and there are non like it. Case and point is, if you are going to throw these type of arguments in my face, then get ready for an article like this. So here we are.

Since an LFO as pulsar could already been made since Reason version 4. You just need to know how an LFO works, and how control voltage works by default. Yes, this will be one of those "it is too much work articles". So if time is your enemy, just use pulsar and stop reading.  

Second reason for me writing down this article is that I recently came back from another discussion where I was told that I should use pulsar as my main LFO. Because Pulsar is the the only LFO out there (I am seeing a trend here, you too?). Just to get this debate over here is an article about Creative LFOs... and why I don't give a crap about those internet people. Nor do I use Pulsar just because it is an LFO.

So, let the slaughter begin (yeah, you had this coming).

Basic explanation on an LFO

As you may have read somewhere on the internet, or on this website (or a basic video about Control Voltages) is that an LFO is nothing more then an oscillator that has a repeating pattern. The pattern is usually that slow, that you can not hear it with the human ear. While in theory if you crank the LFO on a frequency around 440Hz (and track it with the keyboard) it will trigger as a playable oscillator.

If you look at Thor, the maximum frequency of the LFO1 is set to 99.6Hz. So in theory to get close to the KDB range you will need to pick either:

440Hz, 220Hz, 110Hz, 55Hz, 27.5Hz or 13.75Hz.

The closest I currently get at this range is using the 13.4Hz (which is not ideal, just saying that is gets as close to the playable range). So if you set the LFO1 to 13.4Hz and turn on the KBD and route the LFO to the filter you can in theory play the LFO.

Playing an LFO

Now this is not ideal, nor is playing pulsar as a synth. So this already is the counter argument between the two. But this is not the point I am trying to make. The point I am making is that an LFO is a low frequency oscillator that normally can not heard by the human ear. The frequencies are normally too low to hear them. And it basically repeats the same pattern over and over again.

Unless you are a trained human (or super human), you may be able to hear a sine wave playing on the 2Hz. Your brain can pick them up, but your ears can't (in theory that is). But before I am going to turn this in to a psychological article lets just assume that you can't hear LFOs by nature ok?

An LFO is normally used to automate different settings with in an instrument, or as an external control voltage signal. A normal oscillator (lets say a wave table oscillator) would normally go too fast to make it work. However, there are ways you can turn a normal oscillator in to an LFO if you like by playing them on a real low octave. Just saying that is an option and throwing this option on the table just in sake of argument.

Using an Oscillator as an LFO

As you may understand now that an LFO is nothing more then a default oscillator that triggers a low frequency, you might also know that you can use the malstrom oscillators, or the subtractor or Thor as becoming an LFO by default. Only issue with these type of setups : timing them in Hz (or in tempo sync) will become a problem at times. But sometimes you need these type of setups just to create something like an organic type of LFO. Just saying.

The main concept to create these is using a note that goes to the lowest note possible. An easy way to do this is setting up a matrix pattern step sequencer.

Use an oscillator as an LFO

Next up you want to play the oscillator as low as possible while setting up the octave. This can be done with in the oscillator itself.

Oscillator as an LFO

The octave setting is set to 0 in cases like these. Next up you will need to convert the oscillator to a Control Voltage signal. This can be done as the following setup:

Oscillator as an LFO

Alternative route would be using Filter 3 output to CV. While doing this, we have the filter 1 drive as an additional scaler to send out the amount of LFO changes (like the level of pulsar does).

The benefit with these type of setups is that have a lot of different wave forms (hint: wavetables) to turn those in to a unique type of lfo. The position can then be used to alter the shape of the LFO and the drive could be the amount. Only negative part with these setups would be that it has no "sync" method.

LFO Scaling

LFO scaling is a method to scale down the LFO with a different source. If you compare this with Pulsar, this would be known as the "Level". To create the exact same set up as pulsar LFO, you could use Thor and program it as the following:

Scaling an LFO using Thor

LFO2100CV out 1100Rotary 1

In this context we can use the Rotary 1 as a scaler for the LFO. The more the rotary gets opened up, the more the LFO will have an impact on the CV outputs (thus the CV it needs to modulate). In the following example file I am using a Dr Rex loop (again) to modulate the filter frequency of the Rex Loop. I tend to use Rex loops a lot in these articles because it is easy to learn source material. The following file is again a Reason 9.5 example file. 


This brings us to the following: what is lag? Lag in pulsar is nothing more than putting a Low pass filter on top of the LFO itself. The result of this would be that it cuts of most of the hard edges on a waveform itself. While the filter might be different on the Pulsar device, I am using this as clear evidence that Lag is just like using a filter on the waveform:


And this is without lag:

LFO no lag

While the curve with lag will be a bit different between Lag vs LP24 filter. The idea kind of remains the same (maybe it is a LP48 filter, or a LP96 filter even). The LP filter in these cases will have a similar result in to 'cutting' off the harsh edges.

The way I am making this connection work is using the LFO2 to go through Filter slot 3. The audio output gets converted to a CV value using the programmer:

Lag LFO using Thor

Now the biggest benefit behind this setup in particular would be the it can also have a Band Pass Filter, High Pass filter or Peak filter on the LFO itself. And this is partially where things could get rather interesting from an LFO perspective.

LFO Fomant filter

Now I know this isn't really practical from this point of view. But just saying it an option to do it. Hence, creative LFOs right? In the following example file I am using an LP24 filter to act like lag, while enhancing a delay effect using a chorus + delay to add an additional delay on the LFO itself (yeah, lets plug that stuff in there too...)

LFO Phase

LFO and Phase is nothing more then delaying the LFO with x-amount of degrees. The amount in degrees normally is determined by the rate the LFO goes. The lfo by default would get chopped in to 180 segments (if the max amount of degrees would be 180). And by setting the degree it gets delayed with that amount. While there are no stock devices that handle this behavior proper, there are however some things we can do to mimic the idea.

What we can do is use an LFO and delay the LFO with a few milliseconds (by converting the audio to CV using a delay). It will be self explanatory once you have seen the following Reason 9.5 file:


Since I am still writing down about LFOs in Propellerhead Reason, and I am currently only limiting myself with lets say, Thor as being an LFO. What if we bring in our Malstrom for a minute? The Malstrom contains 32 different LFO patterns. While this does not sound like much you can also define it as modulating an LFO with an LFO. Now, plug that shit in there and we have ourselves a lot of different LFOs to create, modify, tweak and do what ever we want to do with it. Visually it will be hard to keep track on those using just "stock devices". And I can truly recommend using something like jrScope (free) or Skope (not free) from the propellerhead shop for these things. Since they will make your life a little bit easier.

The setup would be using the Mod A / Mod B from the malstrom and plug those inside Thor (as being a CV). 

LFO scale to Scale

To make it so (number one) we'll have to program Thor as the following. CV input will become the CV output. But we are scaling it with 2 different scalers. The first one would be CV input 2 (which is an additional external CV from the malstrom) and the second would the Rotary one of Thor.

So in theory we have a level controller to determine how much of the LFO changes are taking place, but at the same time an external LFO controls the LFO amount of changes. Yeah, plugh that stuff in there as well. To have a real benefit from this setup you want to use 2 LFOs that are not equal in time.

scale to scale sources

So for demonstration purposes I am using a Rate on 3/8 and then an additional scale rate on 12/4. Meaning the sine 3/8th gets scaled up and down every 12/4 cycles. This whole concept gets presented in the next Propellerhead Reason 9.5 example file:


With this whole story now on the table, you might be thinking : doesn't make pulsar all this stuff easier? The answer is Yes, it does. However sometimes I want to have more flexibility to make things work in terms of modular routes, creative setups, full control and so on. So sometimes I still go for using Thor as a scaler and using the malstrom as my mainstream LFO. Sure, there are other alternative routes to choose from (Ammo would be one of those). Well, if you plug Ammo this realm, well... there would be no end to the amount of LFOs you could make.

Published on Reason Experts
Written by
Published on Reason Experts
Published: 2017-07-02

Post reply

Post reply

Edit comment


You need to login to post a comment on

Who is Online

Online users:

Registered users:   Anonymous users:   Total: