Frequency dividers and sequencing, how to program 1/4 notes?

VCV Rack
1

Hello there,

I’m discovering the world of vcv rack little by little and already have reviewed the beginner video series of known figure and role model Omri Cohen.

I also reviewed there are some advanced plug-ins that do what I want…

But!

I took the challenge to do all my baby steps using only the built-in VCV rack plug-ins, so I can acquire a good overview of the building blocks of things, and especially why something works and another thing does not work.

I’ve been doodling with SEQ3, LFOs and Scope attentively, I’ve tried to program little sequences I had written on a piano roll. It already was a challenge of itself because I always have to set up the right voltage, the right VCA level, even when using a quantizer to assist me a bit.

And recently I’ve been stuck in the fact I can’t seem to divide my clock to program uneven-lengthed steps. In usual music you got rhythm with the whole note, half note, quarter note, eight note, so on so forth, but in SEQ3 there’s nothing like that to be found, just a master tempo. As I understand, by default the SEQ3 steps are 1/8 notes with tempo 120, because 1/8 x 8 steps = a bar (whole note).

I’ve tried sequencing voltages that equal the freq ratios I wanted, but I’ve came to find modulating a LFO with V/octave output doesn’t multiply the signal, rather adds to it. I’ve then tried modulation with VCAs but I am not sure of what I do, at all, I feel the VCAs only lowered the duration of my clock gates, but the triggers stayed in place.

So, can someone help me understand how to make 1/4 notes and 1/2 notes mixed in with a seq on 1/8 notes?

Thanks

Reference: my attempt to sequence “note lengths” in a SEQ3 resulted in this mess shown on osc (gone wrong). img link

2

Hi!

I hope the beginner series was somewhat helpful :slight_smile: About what you’re trying to do, as always in modular, there are many ways to achieve something like this. For example, you can use one row of the Seq3 to sequence the clock via the tempo CV input. If you, for example, add -1V, it will play twice the length of the step. If you add +1V, it will play half the length. Another way to do this is to use the gates of an additional Seq3 as the main clock. If you have a rest programmed, the second Seq3 will not advance so the note will be longer. Here’s an example patch :slight_smile: I hope this is a good starting point. example.vcv (1.7 KB)

Oh, by the way, this will work also when using an LFO as the clock. If you add 1V, you multiply the rate by 2 so the notes will be shorter. And if you add -1V, you divide the rate by two so the note will be longer.

4 Likes
3

You can also route the v/octave to the LFO through a quantizer with only the root (C) on. This will divide the LFO. The 7th will give triplets and the 5th dotted notes (or it could be the other way around). Although this theoretically only works with just intonation.

edits: made sense of my own bad logic

1 Like
4

oh, thanks a lot Omri for answering me.

yes, the beginner series gave me lots of ideas on sound synthesis and it all connected with things I already was familiar with in VSTs: TripleOsc, NI Massive and ZynAddSubFX come to mind. I’m willing to understand how things work internally. I actually have an idea to emulate synthesis by comb filter in VCV, as is done in u-he’s Triple Cheese… Might be of interest for you too! Triple Cheese user guide.

Your example patch has an upper-left part that’s not connected whatsoever to the bottom and right parts (sound input). It seems like the part with the SEQ you are explaining is in this upper part, as opposed to the trigger-activated clock in the bottom, right?

And also, can you explain again what modulation does exactly? Does it act on the frequency or on the amplitude of a signal? In this example, I don’t get how voltage can become a tempo. Is the “120 bpm” from the potentionmeter on the left still relevant ? If I understand well, adding -1V is diving this fixed 120 bpm tempo by 2? How so? In my understanding it may be that -1V sends a -1Hz signal, and because 120bpm is equal to 2Hz, -1V makes it become 1Hz, hence division by 2, but I am not sure.

oh, I have another little question: how can I make my Scope to only display 1 full cycle of my clock sequence? Is there a formula I can use to correlate the output Hz, and the different steps vs. the ms/screen input?

5

this is worth an attempt but can I also do it sequencially to mix lengths?

6

As @Omri_Cohen suggested, use one row of the seq3 to control the timing of the LFO. Route that rows output through a quantizer (not necessary) and into the LFOs v/Oct input. Then use the output of that LFO to drive the sequencer.

7

Oh, sorry, I should have added some notes. So yes, the two parts are not connected. The upper part is showing how to change the tempo, and the lower part is showing how to use an additional sequencer. About the modulation, in this case, when using it to change the frequency of a signal like LFO frequency or the frequency of the sequencer, it will control the rate. Frequency is basically rate or speed. By adding positive 1V you will basically double the frequency, and adding -1V will half the frequency. This is not always the case but it is true when dealing with the VCV LFO and the Seq3. Another thing important to understand is that everything is voltage. What’s called “tempo” is nothing but a repetitive voltage. For example, if you use an LFO as your clock, you use basically an oscillating pulse wave. The frequency of this wave, its rate, will change the so-called “tempo”. Does this make more sense? I’m not so sure about the scope though. What do you mean by one cycle of the clock sequence? Do you mean the sequence itself?

8

yes. I sometimes find a “sweet spot” on the scope where nothing moves. For example, in a square signal of 2Hz, a setting of 3000ms/screen will output a nice almost static bunch of squares representing 5 iterations of the signal. I wondered if it is a thing that’s predictable.

So the 1V and -1V are completely unrelated to the fact that my basic tempo was 120 bpm, it is a truth that stands at always in SEQ3 and LFos? Whatever the initial tempo, -1V divides my frequency by 2? It just weirds me out that a DC wave’s height (in V) can have any influence on an AC wave frequency (in Hz).

9

OK, I think I will stick to the gates method for it seems a bit more elegant, I guess I can use it along with a sequencer switch. That way all my clocks and tempos stay consistent altogether, other ways of performing seem unnatural to me.

Edit: don’t know what clock to use in the sequencer switch lmao. This is all sorts of finnicky.

Do we agree that in a default 8-step sequencer I have 8th notes of its tempo, and in a default 16-step sequencer it is 16th notes of its tempo?

10

Maybe this quote from the VCV Rack Manual will help - hopefully not bring more confusion.

image
image2226×408 77.3 KB

Voltage Standards - VCV Rack Manual

I found it useful to put this in a google sheet

https://docs.google.com/spreadsheets/d/15dB3SwtIo329Q5CxprQaH5sZULZryCsw0l4A7QLPrt0/edit#gid=0

1 Like
11

Well, no, not really. The length of the sequence doesn’t matter, in this case. Let’s say that you have 120BPM and an 8 step sequence. If you run the sequence with a 1-to-1 clock, it will be really quarter notes. If you run the sequence with a multiplied by 2 clock, it will be 8th notes, and multiplied by 4 will be 16th notes. You will still have 8 steps though. With the Seq3, I recommend starting with a higher BPM as a clock multiplication. For example, instead of 120 go for 240 or even 480. It will still be the same tempo but the resolution is higher. Does this make sense?

1 Like
12

thanks, this google sheet is efficient!

13

There is another way to establish varying note lengths with SEQ3 - set the sequencer to pass through the clock, clock the sequencer with an LFO square wave, and use one of the CV channels to modulate the pulse width, and the step trigger to reset the LFO. The SEQ3 trigger then becomes varying length gates to drive your ADSR. A pulse width of 25% is a quarter note, 50% a half note, 75% a dotted half note, etc. A pulse width of 100% (actually only goes to 99%) is a whole note, but the 1% gap prevents tied notes across multiple steps. But this can be overcome by using a low pass filter as a slew limiter to prevent the 1% dip from triggering the ADSR at the transition to the next step.

I posted a video using this technique:

Check the video description for links to the patch, which includes an explanation for how it works. The video also is a demo of how to create a 32 step sequencer using 5 SEQ3 modules.

If you are sticking with VCV Fundamental modules for now, then you might want to check out VCV Fundamental Constructs, where I have a bunch of VCV selections using only Fundamental modules to implement all kinds of useful techniques.

Finally, the VCV documentation is incomplete and/or out-of-date for the Fundamental modules. I’ve attempted to document a few of them:

Proposed documentation for the VCV Fundamental SEQ 3 module

Proposed updated documentation for the V2 VCV Fundamental Random module

Proposed updated doc for the V2 VCV Fundamental VCA

5 Likes
14

wow, those fundamentals construct look like an amazing idea, I’ll dig into them when I have time.

15

This is very clever. I can’t believe haven’t seen this video yet. The pulse width makes sense, but using the trigger output to reset the LFO is brilliant. If you set the LFO to 1 HZ, I think you can actually work in milliseconds, where 10v = 99%pw =1000ms, 5v = 50%pw= 500ms, etc. I will have to experiment when I get home. Nice.

1 Like
16

yes, that makes sense, if I want my default steps to be faster, I can multiply my clock in SEQ3 by the desired rate.

I’ll be exploring the fundamental constructs proposed by @DaveVenom to understand better how it all falls into place though, because I’m still concerned what gives about the “master” clock that will make sure each sequence switch and similar runs smooth and that I can build a song structure…

Thanks so much for your advice, I’ll keep going.

edit: Just visualized it on the scope and now I get that it was indeed 4th notes.

17

Thanks! I was in the same situation as Marvin (@quantum) wondering how I could vary the note lengths. I wasn’t sure how well the LFO reset and slew would work, and was thrilled when it worked as well as it did.

The technique still has limits - only one note per step, and all notes start on the clock beat. But I do have an extension that should allow notes to start on the off beat, though I haven’t tested it.

  • Split the trigger output into two signals, one normal for the on beat notes, and the 2nd with -10V (from 8VERT) added (MIX module) for the off beats. The off beat triggers will go from 0 to -10V. Use the MIX context menu to invert the result to restore it to a 0 to 10V range.
  • Use a 2nd SEQ3 channel to choose which trigger to use for each step. (That still leaves one channel for pitch.)
    • 10V for the on beat notes
    • -10V for the off beat notes
  • Use a pair of VCAs to control which trigger signal is used
    • On beat: Use the raw 2nd channel as VCA CV, paired with the on beat trigger signal as input
    • Off beat: Use 8VERT set to -100% to invert the 2nd channel and use as the 2nd VCA CV, paired with the off beat trigger signal as input
    • Only one of the above will yield a 10V gate at any time, the other will be constant 0V. Use a MIX to sum them together to get the final set of gates for your ADSR.
1 Like
18

I’d forgotten that you were the maniac behind the Fundamental Constructs, @DaveVenom! Talk about commitment to an idea beyond reason!

I’m intrigued by chaining VCV SEQ3 to make longer sequences. Nysthi Squonk does that by using EOC to stop current sequencer and start the next sequencer in the chain. I’ll have a look at your video.

Best thing about Seq3: It has full range knobs (-10v to +10v). Worst thing about Seq3: It has full range knobs. I generally use a NYSTHI ConstAddMult if I want to have it generate musical notes in the range of human hearing. Seq3 is so useful - and pun intended, fundamental - I wish it had an expander that let you set the ranges.

19

Doesn’t the 8vert do that?

20

The 8vert is a great attenuator, but it doesn’t have an offset. There are a number of modules that have scale/offset in a single module, but no 8 channel Scale/Offset modules. Which would be hella useful!