Starting with the Starter Patch in VCV Rack
When you create a new patch in VCV Rack (under the File menu, just select New), you will likely see a patch that looks something like this:
I don’t know anyone else using VCV Rack so I can’t claim that this is the same on all machines. It is very easy to override the default template patch, for instance by clicking on Save Template instead of Save or Save As:
Unlike in other applications, this template is THE template, as in the patch that loads by default. If you are used to creating lots of templates in your DAW, for example, for different mixing scenarios, don’t import that mental habit into VCV, because in this context ‘template’ means the patch that loads when you create a new patch, and thus there appears to be only one template!
I will keep the first VCV Rack patches on the simple side, to focus on key concepts. Note that there is a special way of sharing VCV Rack patches — if I upload a patch to my Google Drive for sharing, either as a .vcv or .zip file, and then download it, and attempt to open it by double clicking on its icon, I will get the following error message:
The way around this is to first open VCV Rack, and then from within it, open the .vcv patch from within the File menu, and then a patch shared in this way should work. Since there are so many modules available, you need to make sure you have the same plugins installed as the patch uses, and I specify these in the tutorials as well.
I usually find demo patches to be a bit too visually dense to be of pedagogical value (the same often goes for tutorial Max patches), so the first thing I’ll do is space out the elements to see the logic better, and remove unneeded items. Here is the template patch in its spaced out version, which you can download here. It’s the same image as in the top banner, but I am sparing you from having to scroll up to see it again.
The first thing to note is that in VCV, outputs have black rounded corner squares around them and inputs do not. With modules designed by other developers, this convention can vary, and sometimes you’ll just see some other kind of outline around inputs instead of the black rounded square type you see with the fundamental modules you see below.
Thus, what’s happening here is that, at the MIDI input from the hardware keyboard (an M-Audio Oxygen 49) represented by the MIDI-CV module, we are taking three outputs: a
V/OCT (voltage per octave) which is the input to the
V/OCT of the VCO-1 (a single voltage-controlled oscillator, which is the main sound generator), a
GATE, which goes to the
GATE input of the ADSR envelope generator, and an
RTRG (retrigger) which connects to the
RTRG input of the ADSR.
From the VCO-1, which has four wave types available (sine, triangle, saw and square), the
SAW output goes to the main
IN of the VCF (voltage controlled filter). The main
OUT of the ADSR is doing double duty — it is controlling the shape of the VCF (the manner in which frequencies are filtered from the saw wave), and it is also the main volume envelope for each time a sound is produced by the MIDI keyboard. Double dutying is possible in VCV Rack by holding CTRL (PC) or CMD (Mac) to add additional cables to an output. To shape the filter response, its
OUT connects to the
FREQ input on the VCF. To shape the overall volume, its
OUT also connects to the
CV1 of channel #1 of the Mixer. The sound played by the mixer is fed to its
IN 1 from the
LPF (low pass filter) of the VCF.
Finally, the Mixer’s main out
Mix is sending the same mono signal to outputs
2 of my USB audio breakout box via the Audio-8 module, which in my case is a Steinberg UR22. And at the spatial (left-to-right) end of the chain, a Scope allows us to see the visualized waveform from the
CH1 Mixer output which is going to its
From this basic patch, here are the main parameters to explore if you are brand new to VCV Rack.
VCO-1: Because the saw wave is selected, the
PWM CV controls have no effect, because pulse width parameters only make sense on square waves. Move the cable over from the
SQR and then those knobs become useful. Only
P.Width will produce an audible change, since
PWM CV will require an additional modulation source.
ADSR: In more sophisticated synthesizer patches, you will usually have more than a single envelope generator. Here, the ADSR is shaping the overall volume of each note and also the filter response of the VCF. Usually you would have multiple envelope generators, each with a somewhat different timing to produce greater variety or complexity in the sound.
VCF: A voltage controlled filter emulates a common acoustic property, namely that as a sound dies down toward silence, its frequency components also become less bright. I.e. when you pluck a string and it quiets down toward stillness, it is not simply becoming quieter, but there is also a roll-off of the high frequencies over time so that the sound becomes duller as it becomes quieter.
The VCF is probably the most interesting module to experiment with in this patch, because it will produce the widest variety of sonic differences, though how you set up the ADSR values will also play a roll in this. The ‘normal’ way to use a VCF is as I described above — you set the frequency cutoff which is where the filtering commences, and roll off the highs over time from there so that the sound becomes duller as the envelope completes. But with a VCF, you can produce an entirely ‘unnatural’ effect and instead choose to make a sound become brighter over time, because parameter knobs aren’t required to obey the acoustic behavior of real sounding objects.
RES is the resonance of the filter cutoff frequency so having it set a bit on the higher side will help you hear these effects better. With
FREQ CV dialed far to the right, and
FREQ dialed far to the left, you will hear the ‘standard behavior’ of VCFs when controlled by envelope generators.
To produce an opposite and thus ‘unnatural’ effect (which is perfectly natural in the acoustic universe of electronic music!), just reverse those two parameters, dialing
FREQ to the right and
FREQ CV to the left.
REL value of the ADSR becomes much more interesting in this alternative scenario, because for some reason it’s just more sonically interesting to hear tones become brighter over a longer period of time by cranking the
REL up towards maximum, compared to the usual scenario when long release times tend to become annoying since the pitches pile up too much and eventually outdo their welcome.
When twiddling these two parameters of the VCF,
FREQ CV, in opposite directions, also look at the waveform in the SCOPE which will visualize the increase or decrease in the sound’s frequency components.
There’s not much info about the VCF in the online manual (its entry is reproduced below) but hopefully this tutorial has helped you see some possibilities for getting the most out of it.