VCV Rack is a Eurorack simulator with over 2000 free software modules, many of which are re-creations of popular hardware versions. There is a lot of depth here, some far-out designs and a wealth of ideas. Sequencers range from standard eight-step modules to unique designs based on rotating planets and cellular automata. VCV Rack also provides a great introduction to modular synthesis before you decide to jump into Eurorack hardware.
In this Weekend Workshop, we will focus on the Turing Machine module to add randomness to our patches and learn to interact with it to lock in and loop sequences. This will hopefully inspire you to start exploring the world of VCV Rack and the many generative modules available.
We will start with a simple patch and build that up to include a melody of sorts, a bass line and percussion all driven by different aspects of the Turing Machine module.
What you’ll need
- VCV Rack – free download here.
1. Adding Modules in VCV Rack
To add modules, you will need to log in or create an account at vcvrack.com. Go to the Library to browse and subscribe to modules on the website.
After subscribing to a module on the website, it will be available in the desktop application.
A red badge appears in the application when new modules are available. Click ‘Update All’ to refresh your local library. Restart the application if you do not see the red badge.
2. Create a basic patch
Now that you know the process, let’s build a basic patch with an oscillator and filter. The frequency of the oscillator is set by the Scale output of the Turing Machine.
Start by adding the following modules on vcvrack.com and then right-clicking in the desktop application to load them into your rack.
- Impromptu CLKD: provides a tempo-based clock.
- Stellare Music Thing Turing Machine: a random looping sequencer based on the Eurorack module by Tom Whitwell. More about this in the next section.
- Befaco Even VCO: a voltage controlled oscillator based on the Eurorack module of the same name.
- Audible Instruments Liquid Filter: based on the four-pole filter from Mutable Instruments.
- Bog Audio Mix 8: a mixer with pan and mute. This module is not pictured above.
- VCV Audio 8: this will send audio to your audio device. Instructions are available by right-clicking on the module. This module is not pictured above.
Screenshots include the JW-Modules Full Scope module to visualise the Turing Machine output.
Let’s connect the modules to get some sound flowing. Click and drag between outputs and inputs to create a cable connection.
- CLKD: Clk out to Clock in on the Turing machine.
- Turing Machine: Scale out to V/Oct input on the Befaco
- EvenVCO: Ramp waveform out to In on Liquid Filter
- Liquid Filter: LP4>VCA to L In on a Mix 8 Input
- Mix 8: L and R Out to Audio 8 inputs 1 and 2
Twist the large knob on the Turing Machine to get the sequencer started. Adjust the oscillator Octave down to 8’ and play with the filter for a pleasing sound. Reduce the range of notes by adjusting the Turing Machine scale to about 0.22.
The frequency of the oscillator is responding to continuous voltages from the Turing Machine, so they are not locked to a chromatic scale. We will quantise those voltages in the next patch. For now, you should hear free-flowing sounds similar to this clip.
3. What is the Turing Machine
So what is the Turing Machine doing, and how do we interact with it? Everything is based on a shift register which acts as a pipeline for 1’s and 0’s. A series of 1’s and 0’s are shifted through this pipeline on each clock pulse. The last bit gets copied back to the beginning of the pipeline in a circular fashion, but before it is copied, it may be changed from a 1 to a 0 or from a 0 to a 1. The odds of this bit changing are determined by the position of the main large knob. At lower settings, maybe one bit in 10 will be flipped, with the loop changing gradually. At 12 noon, five bits in 10 will be flipped. The loop is filled with random data that never repeats. At higher settings still, every bit will be flipped, and the pattern becomes a Mobius loop.
As the manual says, it is designed as a sequencer that you can steer in one direction or another, not one that you can program precisely. This is what makes it great!
In the next section, we will quantise the Turing Machine output voltage to a scale.
4. Quantising Notes
We can make the patch more musical by adding a pitch quantiser. This will quantise the Turing Machine output to the nearest note before sending it to the oscillator.
We’ll use the ML Modules Quantum since you can specify exactly the notes you wish to allow on the front panel. Add this module to your rack and patch it between the Turing Machine and the EvenVCO.
- Turing Machine: Scale out to Quantum Input
- Quantum: Output to V/Oct input on the Befaco
Enable a few notes on the Quantum front panel keyboard and listen to the difference.
Next, we will add a few modules to improve our sound.
To sweeten our sound, let’s add the Vult Slap envelope generator and the Valley Audio Plateau reverb. The Plateau is a lush sounding plate reverb that will add some depth to our patch. Add the Slap and Plateau to your rack and connect them between the filter and mixer.
- Liquid Filter: LP4>VCA to L VCA In on the Slap
- Slap: L Out to L In on the Plateau
- Plateau: L and R Out to Mix 8 Inputs 1 and 2
- Quantum: Gate out to Slap Gate In
Pan the Mix 8 inputs left and right to get the full stereo effect of the reverb. Reduce the sustain on the Slap to get a snappier sound for the next step. Listen to the sweetened sounds.
We’ll explore another feature of the Turing Machine to modulate the filter in the next section.
6. Modulation with Turing Machine
The five knobs on the right side of the Turing Machine allow you to create a different melodic sequence, related to but different from the main output. This is known as the Volts Expander.
Let’s take the output of the Volts Expander and use it to modulate the filter cutoff to get an idea of how it works. Patch Volts to the Filter.
- Turing Machine: Volts Expander Out to the Liquid Filter Freq Input
Adjust the knobs and notice how the filter cutoff can emphasise different notes of the sequence depending on the combination of settings.
For more variation, we can patch the Main output to the filter resonance.
- Turing Machine: Main Out to the Liquid Filter Res Input
Listen to how the filter changes are related but diverge from the melody. Vary the Turing Machine knob to change the sequence.
We will use another feature of the Turing Machine to control a second oscillator in the next section.
7. The Pulses Expander
The left side of the Turing Machine has seven outputs that correspond to the first seven bits of the sequence. When a bit is on, the corresponding output will produce a pulse. These can be used to trigger modules for rhythmic variations.
Let’s add a second oscillator and a Low Pass Gate that can be triggered to open by a pulse output. Add three more modules to your rack.
- Bog Audio LPG: Low Pass Gate
- Liquid Filter
Patch everything together as follows:
- Turing Machine: Any Pulse Out to Bog Audio LPG Trig In
- Quantum: Output to V/Oct input on the second Befaco
- EvenVCO: Ramp waveform out to Bog Audio LPG In
- Bog Audio LPG: Output to Liquid Filter Input
- Liquid Filter: LP4>VCA to an input on the Mix 8
The Low Pass Gate is only open when it receives a pulse on the trig input, so we get a variation on the sequence, yet it is related. Try different pulse outputs and see what works.
We will use more pulse outputs to drive a drum module in the next section
There are so many different options here. Let’s use two more pulse outputs to trigger drums. Add the Erica PicoDrums module and patch it in.
- Turing Machine: Any 2 Pulse Outs to PicoDrums TR1 and TR2 Inputs
- PicoDrums: Out to a Mixer 8 Input
Vary the Turing Machine knob and explore the possibilities.
This clip uses the same patch with different settings while interacting with the Turing Machine.
More to explore
In a few short steps, we’ve created something that’s both musical and unexpected. If you like the direction this is going, there are many more generative modules to explore including different versions of the Turing Machine. If you want to go even further down the generative rabbit hole, check out Permutation by Grayscale.
Share your results and tell us what tutorials you’d like to see in the MusicTech Creator Community on Facebook.
Check out more Weekend Workshops here.