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How to Create an FM Dubstep Bass in Reason

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Read Time: 10 min

In this tutorial I'll show you one of my methods to get a modern synthetic bass sound similar to those used by artist such as Knife Party, Skrillex, xKore, and many others. At the same time we'll take a detailed look at the creating process of a complex Combinator patch.

Here is an attempt to integrate the patch that we'll build in a dubstep song context.

And this is how its variation sounds after a bit of resampling inside Reason.


We'll create this patch in three big steps:

  • First we have to create an interesting timbre of the sound by frequency modulation (FM).
  • Next we give it a vocal color using filters.
  • Finally we maximize its potential and coolness by adding a little bit of distortion.

Using the same patch I will show you how easy is to customize it to get some nice variations, by making a few changes in the timbre section.

1. Building the Timbre

Step 1: General Setup

All the devices we'll use in this tutorial are initialized by default. To get the same setting go to
Edit > Preferences > General and uncheck Load default sounds in new devices, or you can initialize each one manually.

Initialized patchesInitialized patchesInitialized patches

Inside a Combinator, hold the Shift key to prevent auto routing, and create a MClass Maximizer, a Line Mixer 6:2, and two instances of Thor.

The routing should look like this:

1.1 General setup1.1 General setup1.1 General setup

The mixer is needed because later we'll add the sub bass. As you may guess, the first Thor will actually
produce the sound, and the second one will be used as a modulator.

For the time being, bypass Filter1 of the first Thor so we can hear the unfiltered sound produced by the oscillators.

Filter1 Bypass

It should sound like this:

Step 2: Thor 1 Oscillators

One of the "secrets" of this sound is selecting a proper (complex) waveform which will be modulated by the other waveforms. All the oscillators of the first Thor will be Wavetable Osc.

Set the wavetable of Osc1 to MixedWaves1, octave to 3, and position to 93. This waveform is the key to the sound we want to achieve. Set Osc2 to octave 5, Osc3 to octave 7, and both of them to Basic Analog waveform with the position to 127. They're actually just sawtooth waveforms, but are better defined than what Analog Osc can provide.

1.2 Thor1 Osc config

Also in the Amp Env section, turn the decay and sustain all the way up.

It should sound like this:

Step 3: Thor 2 Oscillators

Osc1 and Osc2 will be Analog Osc and will be used to give the sound some more high frequency presence. Select the sawtooth waveform and octave seven for Osc1, and sine waveform and octave nine for the second one.

1.3 Thor2 Osc config

In the matrix modulation of the second Thor make the following settings:

1.3 Thor2 matrix settup

Sending the Osc1 and Osc2 to audio outputs means that the sound produced by them skips all the envelope sections, amp, and filters.

Step 4: Routing Modulators

Now it's time to do the routing in the first Thor. First let's take care of the frequency modulation part.

1.5 Routing Modulators

As you can see, the amount of FM between Osc2, Osc3, and Osc1 is modulated by the LFO1. This is a great way to add contour and personality to the sound, especially in our case, because we'll have two major parameters that affect the timbre (the amount of frequency modulation and Filter1) modulated by the same source, LFO1. Also, LFO1 will be used later to modulate the sub bass.

It should sound like this:

2. Filters

Step 1: Setting Up the Filters

The idea is to create a movement of the frequency knob, which will cause the vocal color to appear due to the high value of the resonance. First, make sure that Osc1 is enabled to Filter1 and Filter2. Both of the filters will be State variable filters set to BP12 .

This is a regular band pass filter, and both filters will have Env and Vel rotary turn down to zero. The first filter is the main one because it is the cause of the vocal timbre. Set its frequency to 143Hz and resonance to 97.

1.4 Setting up the filters1.4 Setting up the filters1.4 Setting up the filters

The second filter must pass through the Amp section. Its contribution is to smooth some high frequencies of the sound. Turn its Drive to 26, frequency to 449Hz, and the resonance to 83.

It should sound like this:

Step 2: Routing Filters

Now, in the right section of the modulation matrix, do the following routing:

1.6 Routing Filters1.6 Routing Filters1.6 Routing Filters

Notice that on the third line the gain is modulated by LFO1 to add even more contour to the sound, and also notice that the modulation amount is scaled by Rotary1. In this way we can link the gain modulation to one of the Combinator's knobs.

It should sound like this:

All the modulating oscillators that affect the carrier (Osc1) are set to different octaves and have different amounts. In this way the carrier generate a pretty decent range of harmonics. It's important to start with a well-calibrated timbre.

Step 3: Adjustments

Let's add some more personality to the sound by activating the Shaper and turning the Drive knob to 32. The default Soft clip is good to go.

Turn the LFO1 tempo sync button on and the rate to 2/4. I found that the best result I can get from this patch is to leave the key sync off. That means every time you trigger a MIDI note the position of the filter will change in the spectrum (limits) of the selected waveform. This will cause the sound to start in different phases of the vowel.

To understand better this idea take a look to the picture below:

Graphic waveform exampleGraphic waveform exampleGraphic waveform example

Explanation: This graphic is an example of two possible phases that may occur when you play a MIDI note. The sine shape describes the movement of the parameters modulated by the LFO1. Note that it's flipped horizontally compared to the sine shape shown at the LFO section. This happens because the modulation amount between LFO1 and its destination has negative values, which cause the polarity of the waveform to reverse.

Tip: Experiment with the LFO waveforms and try to resample to keep only the best parts.

Activate the Chorus and reduce the Dry/Wet to 20. In this way the sound is starting to gain a bit of activity in the stereo field.

1.7 Adjusments

This is what it should sound like at this step:

3. Distortion

The filtering process gave to the bass a nice roar, but also made it very muddy. Usually, when filters are used to make this kind of bass, the overall volume and high frequencies are diminished. Through distortion we'll add more clarity to the sound due to the mid-high and high frequency that will be generated based on the low ones, and increase the volume.

Step 1: Scream 4

Create two instances of Scream 4. Bypass the second instance until we need it. That way you'll more clearly notice the effects of the first type of distortion, without interfering with anything else.

For Scream1 set the Damage to 39, the damage type to Overdrive, P1 to 127, and P2 to 20. Turn on the Cut section and reduce de mids to (-22).

2 Distortion Scream12 Distortion Scream12 Distortion Scream1

It should sound like this:

That's a lot better, but it's still messy.

Enable the second unit of Scream 4, turn its Damage to 31, and damage type to Tape. This will focus more on the mid-high and high frequency. Make P1 all the way up and P2 to zero. Again, enable the Cut section and reduce the mids to (-17).

2 Distortion Scream22 Distortion Scream22 Distortion Scream2

It should sound like this:

After this process the sound has clearly a more natural tone.

Step 2: Pulveriser

Now is time to "unleash the beast". Create two instances of Pulveriser, and bypass the second one like we did in the previous step.

The first Pulveriser brings the most amount of distortion onto the scene. Set its Squash to 75 and Dirt to 107, Peak to 29, and the balance between dry and wet signal to 110.

2 Distortion Pulverizer12 Distortion Pulverizer12 Distortion Pulverizer1

The second Pulveriser is used just to brighten up the sound. Change the order in which the signal is processed to the second option. Bring the Peak to 36, Dirt to 16, and Tone to 116.

2 Distortion Pulverizer22 Distortion Pulverizer22 Distortion Pulverizer2

It should sound like this:

4. Fine Tune

So far so good! Now we'll attenuate the side effects of distortion by equalization.

Step 1: EQ

Create two MClass Equalizers. To the first EQ enable Param1 and Param2.

 MClass EQ1 Frequency Gain Q
Param1 313.8 -6 2
Param2 883.9 -6.3 5.7
3.1 EQ 1 and 23.1 EQ 1 and 23.1 EQ 1 and 2

For the second equalizer enable Param1Param2 and the High Shelf.

 MClass EQ2 Frequency Gain Q
Param1 263.5 -7.7 2.9
Param2 631.1 -5.1 3.7
High Shelf 6k 4.3 0.62

It should sound like this:

A good sound—or a good equalization of the sound—is mostly subjective. Feel free to experiment with all
these parameters to your own taste.

Keep in mind that usually an individual final EQ of each sound (or instrument channel) is made, to attenuate the overlapping frequencies in the song context. So again, there are many variables that can influence the EQ process of an individual sound.

Step 2: Stereo Imaging

In this process the best way to get a good result is the "classical" way. I like to keep the low frequencies mono and the treble stereo.

For example, take a look at the image below of my current chain of Stereo Imagers.

3.2 stereo imagers3.2 stereo imagers3.2 stereo imagers

There is no need to set the parameters to a specific value, just turn the frequencies below 200Hz to mono, and expand those which are above 2kHz.

It should sound like this:

Step 3: Adding Sub Bass

Return to the Line Mixer 6:2 and create a third Thor unit under it. Make sure Thor3 audio outputs are routed to the second channel of the mixer. Flip the rack, and route the CV1 Output of the first Thor into the CV1 Input of the third (sub bass) Thor, as in the image below:

3.3.1 CV mod3.3.1 CV mod3.3.1 CV mod

CV1 is now carrying the signal from LFO1, and we'll use it to modulate the amplitude of the sub bass sine wave. All we have to do is to generate a tone at low pitch and make it interact and compile with the rest of the sound.

Inside the third Thor make the Osc1 an Analog Osc with a sine waveform and set its octave to 3.

3.3 Thor3 (subbass) osc

In the matrix, we'll make the sub bass to follow the same movements as the main sound.

3.3.2 Thor3 matrix

5. Macro Knobs

When I consider automating a parameter, I personally prefer to link it to the Combinator's rotaries to keep the tracks more organized. In this case, all the parameters that I would like to automate (some of them mentioned above) come from Thor1.

To link the knobs, open Combinator's programmer section (Show programmer), select Thor1 from the devices list inside Combinator, and select the targets as shown in the image below:

4.1 Macro Knobs4.1 Macro Knobs4.1 Macro Knobs


Rename each rotary properly to avoid confusion.

This is the main patch. Experiment with different waveforms, LFO rates and pitch bend.

Patch Variation

By "patch variation", I mean making a few (minor) changes of the patch's parameters to achieve a slightly different sound that is still related to the original patch. By alternating them you can create better and more complex bass lines.

For example, in Thor1, change Osc2 octave to 3 and, Osc3 octave to 5. Also change the shaper mode to Sine.

Variation example

It should sound like this:

In this way, it is actually really easy to bring some diversity in your composition starting from a single patch.


To get the most out of this patch, experiment with different LFO waveforms and rates, pitch bend, modulator octaves, and resample. In the resource files (which you can download from the top of this tutorial), I include the resample project of both previews.

I hope you've found this tutorial useful. If you have any questions or suggestions, please put them in the comment section below.

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