Building a New Bass Synth With Reaktor Blocks

I am preparing a bass synthesizer for a new eerie electronic project. The project is still in an early stage and things are in flux, but watching people with eurorack hardware on YouTube made me want to patch together my own instrument. Unfortunately, I am not in a place where I can afford to get addicted to eurocrack and go to software that I own instead.

Initial Concept

For the EP, I am aiming towards an eerie electronic vibe with lots of heavy bass that really has some “gravitas”. The instrument should be designed in a way to be MIDI-playable with 2-4 macro parameters, steering the main characteristics of the instrument.

My very first thought is to take two different harmonic rich oscillators and implement some kind of panorama-spread. Depending on the macro-CV, the bass synth either sounds mono or stereo.

A second characteristic I want to include is some nasty drive that adds even more harmonics. This could mean that I need to include a final low pass filter since it is supposed to become a bass synth after all. The amount of drive could be a second macro parameter to be used for emphasize in intense parts.

I have a couple of more ideas how I could shape this foundation synth, but since my experience on modular synthesis is sparse, I want to start patching.


Here is a block diagram of the instrument in Native Instruments Reaktor:

Diagram of Reaktor Blocks patch

Blocks diagram

It takes a bit of time to read these, but the general concept is not too complex. The bass synth consists of roughly 5 sections:

  • Input/Output, consisting of the MIDI “Note in”, the macro knob and mixer blocks – which are all painted black.
  • Two oscillators with two cross fade blocks to dynamically duplicate the signal for the left and right channel. Both channels have their own high cut filters.
  • A parallel distortion module to distort the stereo pan section of the synth.
  • A third sub-oscillator to add some bass foundation.
  • Various VCAs that are all addressed by the same ADSR module to shape the time evolution of the sound.

The front panel looks a bit more chaotic, but there are shiny digital knobs to play with:

Front panel of Reaktor Blocks patch

Blocks front panel

I do not want to have a too complex instrument. The sound can be complex and have many layers, but playing it should be really simple.

Right now I am only using the MK 1 knob to adjust the stereo-width of the synth. Dialed down, everything is mono and sounds like this:

If the knob is turned up, both cross fade blocks are gradually moving the oscillators to opposite sides:

The other thing I dial manually are the three channels in the Mix 4 block. Channel two adds the third sub-oscillator which gives the sound a bit more punch:

Channel three adds a heavy distortion of the main oscillators in parallel:

Putting everything together we have:

Now this is really extreme. How much I will make use of this, really depends on how the music turns out to be. But I think this is a nice and heavy starting point.

Next Steps

The sound is really harmonic-rich and needs additional filtering to be a bit less aggressive and in your face. Depending on where the emphasize in a given song will be, I might even crank every knob to a 100%.

I am also curious if I can add some harmonic resonant filtering. It might be nice to build a second MIDI route to change the note of the harmonic resonance and play the same instrument in two registers at the same time.

All of this needs testing in real music and I do not oppose the idea of throwing everything away if it does not find its place. This is a process.

Toying with a heavy bass synth design for a new eerie electronic music project. Its panorama spread and amount of distortion are adjustable by single knobs.
Want to comment? Send a mail to