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

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).

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?

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

VCV Manual - Voltage Standards

I found it useful to put this in a google sheet

VCV CV to BPM - Google Sheets

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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?

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thanks, this google sheet is efficient!

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

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

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.

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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.

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.
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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.

Doesn’t the 8vert do that?

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!

Yes I agree, I’ll usually turn to bogaudio offset for this task.

But there is:

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Here is my crude attempt at a sequencer:

First row is step length, second row is gate length, and third row is ratchet. The quantizers just round everything off to 1, 1/2 or 1/4 multiplying or dividing. By adding more notes on the quantizer you can add more sub divisions, but the quantizer needs to be set to just intonation.

Here is a test I did using this idea:

[Expeditions in Space and Time - #14 by auretvh]

A second sequencer needs to be added for pitch, velocity, etc.

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It took me a while to figure out what the ratchet CV was doing - which is weird, because I was already thinking about the possibility of using multiple LFOs.

Not sure how well it applies in your patch, but it might be easier to use OCT instead of QNT to perform rounding. Simply patch your signal to the CV input, leaving the V/Oct input empty, and it will round your signal to the nearest integral volt. If needed, you can then attenuate to get nice fractional values, without having to worry about just intonation.

In case others don’t know how easy this is, I’ve shown how this can be done below. the top SEQ 3 is the master, and the bottom will always remain in sync (disregarding the 1 sample delay). Note the bottom STEPS is set to 1, and the STEPS CV to 100%. The only trick is to make sure they start out with the same RUN state. Once synced, they will remain in sync as long as you never interact with the bottom RUN or RESET buttons, or STEPS or STEPS CV knobs.

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Of course, OCT makes so much more sense. Thanks for taking the time to review it Dave. I just like the idea of using a quantizer because of that experiment in the link above. But in this case, it’s pointless. I love trying to figure out things like this in VCV, like a type of a challenge. Which is also why I appreciate all the work you have put into the fundamental constructs. It’s quite a bit of work. :+1:

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hi again Dave,

Is there a way I can visualize what I’m doing and if I am correct or not? I tried the scope connected to the CV1 output of sequencer but it is tricky to observe whether I really have the lengths I want or not because I can’t seem to find the period in which my whole sequence freezes in on screen. And even then it is an unexpected result.

I’m also at loss how to keep an idea of “master” tempo, the tempo of the song that does not change regardless what clock division I give to each individual step.

This is the setup I’m trying right now, just for simple visualizing. In my reasoning, the “master” tempo is the one of the built-in clock of the first sequencer, and my note ratio is given by the LFO’s modulation. I also believe the LFO main knob should be set at the same frequency as my master tempo (2Hz=120bpm).

So as said the first sequencer commands my ratios, it has 2 steps: -1V and 1V to half and double my tempo as Omri explained.

Second sequencer has 2 steps: random voltages but I chose them negative and positive so I can see the change easily.

But it show inconsistency for a reason I can’t find. I have a rather hilly output while it should be one long up and one short down. What am I missing? Is it because I actually didn’t need that LFO in the middle? Getting desperate here because it is so simple and yet I can’t predict its behaviour. Thanks…

I don’t see how that design can possibly work. If you want a sequencer to modify the tempo, then it must modify its own clock, not that of another sequencer. Your design will not work properly whenever you speed up or slow down:

  • If you slow down (half speed), then the master will move on to the next step before the subordinate has completed its cycle.
  • If you double the speed, then the subordinate will always play two notes before the master can move to the next step and establish a new tempo.

You also have an issue that your master clock and subordinate clock will almost surely be out of phase. Assuming other problems are resolved, you would need to reset the subordinate clock whenever the master starts or resets.

Regarding my design from my first post - I think I threw you off. My technique is all about modifying the width of each gate, but at a constant frequency or tempo. So rather than talk about 1/8 notes, 1/4 notes etc., it is better to think of it as playing some notes as staccato, some as marcato, some as legato, and some as slurred. In order to get slurred notes, a slew limiter is needed because the VCV LFO cannot do 100% pulse width.

Say each beat represents a 1/4 note. If you set the pulse width to say 25%, then that might be considered a staccato 1/4 note. You could also say it is a 1/16 note, but then it would always be followed by a dotted 1/8 rest. (unless you implement ratchetting as Auret demonstrated)

I would say 50% PW could be marcato, and 99% legato.

If you need slurred, then you need to add a slew limiter (low pass filter can work), and then 99% would be slurred because the slew would prevent the 1% drop from falling low enough to allow a new attack on the next beat. Legato would then be something like 90%.

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