VCVRackTutorial: Using Multiple Waveshapers to Drone.

Making drones is fundamental to modular synthesis, as it removes pitch from the equation, and makes piece all about timbral texture. This started out as a simple test of various waveshaper modules.

http://cornwarning.com/chaircrusher/Chaircrusher-ShapedDrone.mp3

The patch is here: http://cornwarning.com/xfer/VCV/ShapedDrone.vcv

The core of this patch is using waveshapers to generate harmonically rich distortions of the original sine wave. Since the different waveshapers get mixed, and because they’re all processing a signal of exactly the same frequency, they interfere and reinforce each other. The sound changes restlessly and chaotically over the course of the recording, and you occasionally get ghost notes made when more than one overtone series collides.

The audio signal flows from left to right basically, feeding 4 waveshapers that get mixed and modulated by the keyframe mixer. This is a really good beginner’s patch.

I’ll describe the patch left to right. I liked that it fits mostly in one row.

LogInstruments Precise DC Gen

The DC Gen is used to choose a constant note to send to the fundamental oscillator.

Vult Caudal Mechanical Chaos Source x 2

This module is based on modelling a triple pendulum. Each output represents an arm in the pendulum’s position and velocity. Basically it sounds random but there are predicatable — if chaotic correlations between each output. These are hear to screw with the parameters on modules to the right.

4 x Different Waveshapers

I wanted to check out various waveshapers — the Lindenberg VC Waveshaper, The Vult Debriatus, Lindenberg West Coast VC Complex Shaper, HetricCV Waveshaper . They each have their controls modulated by the Caudals.

Audible Instruments Keyframer/Mixer

The Keyframer is being used a mixer, but it’s unique in that you can record a bunch of different frame volume combinations (as keyframes) and then morph between them, either manually (with the big knob) or by modulation, also coming from the Caudal.

NYSTHI 4DCB

This is a DC Offset remover, and it’s there because waveshaping can introduce a DC Bias that messes with a signals apparent volume (and also messes with speaker cones). This is used between each waveshaper and the keyframe mixer.

Southpole Balaclava Quad VCA

To introduce some variety in the patch, the VCAs are used to modify the level of the signal. This is tuned to be mostly a slow throbbing.

AS DelayPlus Stereo Fx

What’s a modular patch without some delay or reverb? This stereo delay is tuned to long delays (on the order of seconds) so that the live signal is combined with the delayed signal. This adds some fat to the signal, and also introduces stereo panning.

Southpole Balaclava Quad VCA + Vult Knobs

This is just a way to do a master volume knob.

VCVRackTutorial: The Turing Machine


The patch file: http://cornwarning.com/xfer/VCV/TuringMachineExample.vcv

Audio Example: http://cornwarning.com/xfer/VCV/TuringMachineExample.mp3

The two implementations of the Turing Machine Sequencer — in the case of this patch, the one from the Skylights plugin — are not immediately understandable without doing some reading of manuals, which is never anyone’s favorite activity.

Turing Machine sequencer have a property that is one of the best about modular synthesis (or in fact music in general) in that it takes a single simple idea and implements it in a way that can have surprising and musically useful results.

There’s a full document describing what the Skylight folks implemented here, but I think I can describe it very simply.  If you look at the byte symbol above, it shows how it is comprised of bits.  A particular sequence in the Turing Machine uses this byte (or 16 bit word, maybe) in two ways.

  1. The bits are rotated in the buffer.  And by ‘rotated’ I mean that each bit is shifted left, and the last bit on the right  is placed in the leftmost bit location.  This makes sense if you visualize it physically. If you had a row of black & white marbles, you take out the rightmost marble, and place it in the leftmost position, shifting all the other marbles right one space.
  2. In computing a byte is two things: a collection of bits, and the representation of a number in the range of 0 and 255 (or often, one of the ASCII characters).

The Turing Machine Sequencer uses those two representations to generate a pitch and a gate signal. The pitch is the numeric value of the byte, and the gate signal goes from zero to one when the rightmost bit is one.

That’s all that really happens, except for what the LOCK knob does.  When the knob is fully counter-clockwise, every time the sequencer receives a clock, every bit in the sequencer’s byte is replaced by a new, random value.  When the knob is at 12 O’Clock, half of the bits are randomized.  When the knob is fully clockwise, the sequence is locked, and none of the bits change.

So when you use the Turing Machine as a sequencer you have a choice between an always changing random sequence, an unchanging sequence, and a sequence that changes gradually over time.  This example patch comes with a locked sequence that sounds like a classic analog sequencer patch from Kraftwerk or Tangerine dream.

The output of sequencer is a tunable combination of chaos and order. It follows a very musical paradigm.  If the LOCK knob is somewhere around 3 O’Clock it means that the sequence playing changes very slowly a note or two at a time.

It also has one of  most charming features of modular synthesis: Because of how the pitches and triggers are generated, the pitches and triggers have a deep structural relationship.  A change in underlying data byte changes both the pitch and trigger in a predictable way. Well, mostly predictable, as it does it’s magic by random, probabilistic bit flipping.

When two things in music have that kind of relationship, where they’re both tied to different views of the same input, it’s something you can hear.  The sound of the SkyLights Alan Turing machine is the sound of that relationship.

Another about this patch is the quantizing setup of the pitch output of the Turing Machine:

The pitch coming out of the Turing Machine changes at every clock step, so I run it through a sample & hold triggered by the gate output of the Turing Machine.  This means that the note only changes when a new note is triggered.  Then it’s quantized by VCV Scalar.  I’ve selected notes that are a sort of 5 note scale, but different than the standard pentatonic scale.  This is followed by a Fundamental Octave module, that transposes up or down by one or more octaves.

This is kind of a standard setup for most sequencers that I use, because I want things to add up musically, and I want one pitch per note. You can certainly bypass the sample & hold and go directly from the sequencer to the Scalar Quantizer , if you want the effect of the note pitch changing as it decays.

VCVRackTutorial: Using modulated delay times in VCV Rack

This is a method of patching and modulating delays I find so compelling I felt moved to write about it. This is all done in the software modular system VCVRack, and assumes you have a basic working knowledge of it. It involves the VCV Router plugin, which is non-free plugin from the makers of VCV Rack, but I consider it a mandatory purchase.

As a start, consider this simple patch:

VCV Rack Patch (right click or command click to save)

This is a single voice sequenced by a Fundamental SEQ-3 Module. Clock triggers sequencer, clock sends pitch to oscillator and gate to envelope. Envelope modules volume of oscillator signal via a Fundamental VCA-1. The only remotely complicated part is in the middle where the pitch signal is captured in a Sample & Hold, triggered by the gate from SEQ-3. It’s then quantized by a JW Quantizer and transposed by a Fundamental Octave module.

Now, add a delay. In this case an AS Delayplus:

VCV Rack Patch (right click or command click to save)

This sounds fun, and you can play with delay time and feedback. As it happens this delay module models actual analog delays to the extent that changing the delay time affects the pitch of the delays. If you load this patch you can hear this by turning the delay time knob.

What I’m interested in here is to set up a tempo synced delay. The AS BPM TO Delay Calculator can help out there. Drag the delay time all the way counter-clockwise (it will display 1 MS) and then feed the output of a particular delay time from the BPM Delay/MS Calc:

VCV Rack Patch (right click or command click to save)

Now the delays fall in the rhythmic grid, in this case, a dotted quarter note after the dry signal from the VCA. The fun begins when you modulate the delay time. In this case I use 4 different outputs from the BPM Delay/MS Calc, for dotted half notes, dotted quarter notes, dotted 8th notes, and dotted 16th notes. You can select different delay times by clicking on the ‘Clock’ button on the Fundamental Router 4:1.

VCV Rack Patch (right click or command click to save)

Now comes the fun part. I add a Hetrick Random Gates module, and send it the gate output of the SEQ-3 to trigger it. I also turn down the Max knob on the Random Gates so that only gates 1/4 are triggered. I then feed the first 4 trigger outputs on the Random Gates into the ‘Sel’ inputs on the Router 4:1. What is the result? Every time a new note is triggered by SEQ-3, a different delay time is randomly selected.

VCV Rack Patch (right click or command click to save)

What is the result? Something rhythmically and harmonically interesting — it’s continually changes, and each time the delay time changes, it changes the playback speed and pitch of the delayed signal. Now, since we chose 4 differented dotted note delay times, they each have a relationship that is both harmonically and rhythmically coherent. A dotted 16th note is 1/8th as long as a dotted half note, and if you switch between them, the frequency jumps by a factor of whole octaves. In the case of dotted 16th to dotted half note, the transition drops the pitch by 4 octaves. If you haven’t considered the math involved it’s exponential: Twice the time or frequency, increase by one octave, 4 times the time/frequency, increase by two octaves, etc.

It gets even more interesting if you don’t choose delay times that are multiples of each others. Say, use dotted 1/2, quarter note, dotted 8th note and 16th note. The dotted half note is 3/2 the time of a 1/4 note, a dotted 8th is 3/2 of a 16th note. Now as it happens, the pitch releationship of 3:2 is a major 5th, so when the delay time changes it also changes the pitch by an interval that is musically interesting! I haven’t worked out all the pitch relationships between different note durations, but listening to the output, it always seems to add up harmonically, no matter which note duration you choose.

Here’s an example of the output of this last patch. While recording, I tweaked the sequence a little bit as it played.
Download audio file here (left- or command-click)