Achieving simple quarter tones in Eurorack

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wuff_miggler
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Achieving simple quarter tones in Eurorack

Post by wuff_miggler » Fri Feb 21, 2020 10:27 pm

Hi Wigglers,

My first tech post here. Be gentle :D

I am trying to spec out my first modular which is loosely based on the Doepfer Trautonium example:

Image

One thing I would like to do as i wish to perform middle eastern traditional music on this set up. I would like to Quantise the starting notes which can then freely slide whereever they please - raising any note by a quarter tone on oriental workstations is done by little buttons arranged like a keyboard:

Image

Now....im thinking to achieve this i will need:

a)Doepfer Precision Adder. A185-2
b)Doepfer Dual Quantiser? A156 QNT?
c)Doepfer A-173 Micro keyboard/Gate Module. (?? unsure about this one)

Can anyone help get me in the right direction as i am not sure how the above can or if it even will work together to achieve desired result! :D
Last edited by wuff_miggler on Fri Feb 21, 2020 11:50 pm, edited 1 time in total.

adaris
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Re: Achieving simple quarter notes in Eurorack

Post by adaris » Fri Feb 21, 2020 10:51 pm

FYI, your title says quarter notes rather than quarter tones. But anyway, I think the Disting Mk4 is probably your friend here. For one it has a programmable quantizer that I believe can be used to quantize to any scale you can imagine. I haven't used it yet, but I'm sure other people on here have experience with it. Disting also has a precision adder that you could use in conjunction with the Doepfer A-173. You'll need to attenuate the CV coming out of the A-173 though if you want it to go in quarter tone steps instead of semi-tones, and I'm thinking the attenuator would have to be exponential in order to divide every semi-tone in half.

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wuff_miggler
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Re: Achieving simple quarter tones in Eurorack

Post by wuff_miggler » Fri Feb 21, 2020 11:56 pm

HI Adaris - i fixed my post to correct quarter note to quarter tone - thanks for picking that up.
Wow the disting looks like an incredibly useful utility module! Thanks for the tip.
Would like to know if anyone has used it for this purpose :-)

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Re: Achieving simple quarter tones in Eurorack

Post by zerodivide » Sat Feb 22, 2020 12:04 am

you need a clock divider, that spits out divisions of your main clock. quarter notes, 8th notes ,16ths, etc
I would look into Pamela's new workout!

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Re: Achieving simple quarter tones in Eurorack

Post by wuff_miggler » Sat Feb 22, 2020 12:38 am

thanks for chiming in Zerodivide - your username checks out :P
I just edited the subject to fix it so it's about microtuning :-)

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Taylor
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Re: Achieving simple quarter tones in Eurorack

Post by Taylor » Sat Feb 22, 2020 1:33 am

To get quartertones, you really only need to quantize to semitones and then attenuate the resulting voltage by half, which at its most basic can be done with a passive attenuator. The same principle can get you to 36 TET or whatever other equal temperaments you may want to experiment with.

The more nuanced aspect is quantizing at the note onset but then allowing the ribbon to output continuously-varying voltages for your pitch bends. One approach I tried in the past is to use a sample-and-hold to sample the note with the gate coming from the a-198 and add this to an inverted copy of the raw ribbon voltage. At this point the result of this addition would be 0V, but if you then bend up or down while holding the ribbon down, you get a continuous pitch bend voltage that you can add to your VCO's FM input.

Also, it's sorta OT but since we're on the topic... I will never pass up a chance to show my bass with quartertone frets!

Image

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wuff_miggler
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Re: Achieving simple quarter tones in Eurorack

Post by wuff_miggler » Sat Feb 22, 2020 2:55 am

Hi Taylor - thanks for your input!

So - from what you're saying i'd need a dual quantiser A-156 in the example diagram....then - i'd need to apply passive attenuation with something like module A-183.

With the passive attenuation - something i dont understand is...lets say im aiming for an A4.... and the Quantiser locks in for example at note A4...if i apply blanket overall attnuation - will that not then just give me a 12 tone scale which is 50cents off tune? How am i getting to double the notes using this method?

PS. that bass is sweet!! i've had a yard sale piece of shit guitar sitting in my garage for 10 years. I really should yank those frets off and have fun with that thing!!

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Re: Achieving simple quarter tones in Eurorack

Post by Ebotronix » Sat Feb 22, 2020 3:17 am

microtonal quatertone scale by Quantimator (chromatic) to
A185-2 input with attenuator for 0,5V / octave scaling

I used the Quantimator in this vid but it also works with the A 156 .
the A 185-2 was behind the Quantizer (chromatic scale to A 185-2 attenuater input )



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Re: Achieving simple quarter tones in Eurorack

Post by Arneb » Sat Feb 22, 2020 5:00 am

wuff_miggler wrote:
Sat Feb 22, 2020 2:55 am
With the passive attenuation - something i dont understand is...lets say im aiming for an A4.... and the Quantiser locks in for example at note A4...if i apply blanket overall attnuation - will that not then just give me a 12 tone scale which is 50cents off tune? How am i getting to double the notes using this method?
The way 1V/oct works, attenuating by 50% would squash two octaves' worth of 12-tone quantized voltages into one octave's worth of 24-tone quantized voltages. So, in principle, it would work.

In practice, a passive attenuator would not be precise enough for your purposes, I'm afraid.

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Re: Achieving simple quarter tones in Eurorack

Post by wuff_miggler » Sat Feb 22, 2020 5:13 am

hey Arneb - thank you for clarifying - i thought a rough knob wouldt accurate enough. im thinking i will need a module that allows me to load scala files.

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Re: Achieving simple quarter tones in Eurorack

Post by fitzgreyve » Sat Feb 22, 2020 5:25 am

Arneb wrote:
Sat Feb 22, 2020 5:00 am
The way 1V/oct works, attenuating by 50% would squash two octaves' worth of 12-tone quantized voltages into one octave's worth of 24-tone quantized voltages. So, in principle, it would work.

In practice, a passive attenuator would not be precise enough for your purposes, I'm afraid.
Was about to say roughly the same thing - in principle all that's needed (for the ribbon input) is a semitone quantizer, followed by "divide by 2" (or if you prefer "multiply by 0.5"). THe same is in essence true of any equally tempered scale - just semitones followed by "divide by N".

As Arneb indicates, a simple passive attenuator (module) could have pitch tracking issues - how well it tracks will possibly depend on the exact output characteristics of the module feeding it, and the input characteristics of the input it feeds to.

Looks like most of the VCO's in your rack above already have an input with an attenuator (mostly "CV2"), which just needs setting to 50%. There should be no (or minimal?) pitch tracking issues as these attenuators are part of the VCO modules, but it will depend on accurate setting of the attenuator, which is then then potentially vulnerable to getting moved off setting.

Does anyone make a "precision attenuator" ? - something like a 10-turn potentiometer with lockable 10-turn knob, with a (correctly designed!) buffered output and possibly buffered input as well. Easy to do if into DIY.
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Re: Achieving simple quarter tones in Eurorack

Post by wuff_miggler » Sat Feb 22, 2020 5:29 am

I will check out doepfers modules for a divider. The quantiser module i mentioned above followed by divider sounds like the answer :)
Thank you fitzgreyve!

EDIT:

This is what you described - but not fine enough.

Image

and it says "Audio frequency" divider. hmmm...ill need something with LCD and with 0.50 or finer increments.
Last edited by wuff_miggler on Sat Feb 22, 2020 5:37 am, edited 1 time in total.

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Re: Achieving simple quarter tones in Eurorack

Post by fitzgreyve » Sat Feb 22, 2020 5:37 am

Just to be clear - it should work OK only using the CV2 inputs on the VCOs in your rack, but is sensitive to accurate setup, and then not being moved.

THere are buffered attenuator modules available (possibly not by Doepfer?) , but IMO they won't give any significant advantage over the VCO CV2 inputs.

EDit - THat's a pulse divider, you need a CV attenuator (sorry if my terminology was inconsistent).
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Re: Achieving simple quarter tones in Eurorack

Post by wuff_miggler » Sat Feb 22, 2020 6:01 am

All good fitzgreyve, i understood you :-) thats why i put inverted commas around "audio frequency" haha.
Looks like i will end up mix and matching modules. I thought going all doepfer would be cool for a first rig - i guess not so important if i want to get this things performing to my requirements :-)

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Re: Achieving simple quarter tones in Eurorack

Post by synonymist » Sat Feb 22, 2020 8:49 am

wuff_miggler wrote:
Fri Feb 21, 2020 10:27 pm
i wish to perform middle eastern traditional music on this set up. I would like to Quantise the starting notes which can then freely slide whereever they please...
Hello. Consider using an Ornament & Crime module.
Last edited by synonymist on Sat Feb 29, 2020 1:01 pm, edited 1 time in total.

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Re: Achieving simple quarter tones in Eurorack

Post by analogsplitter » Fri Feb 28, 2020 4:14 pm

I have to think more closely about the techniques mentioned here, but I was wondering if the same concept would work in order to get a 31 per octave scale out of a quantizer?

I know that if you attenuate the cv output of a keyboard that has CV out, you can expand the numbers of notes per octave (you would end up using 31 of the keyboard keys to get a 31 note scale]. But I’m not sure if it works this way with the quantizer.

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Re: Achieving simple quarter tones in Eurorack

Post by electricanada » Fri Feb 28, 2020 4:28 pm

wuff_miggler wrote:
Sat Feb 22, 2020 2:55 am
Taylor - thanks for your input!

PS. that bass is sweet!! i've had a yard sale piece of shit guitar sitting in my garage for 10 years. I really should yank those frets off and have fun with that thing!!
Take them off. Use old nylon guitar strings tied around the neck for frets. You can slide them into whatever tuning.
Eléctrica (electric) Nāda (the yoga of sound).

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Re: Achieving simple quarter tones in Eurorack

Post by wuff_miggler » Fri Feb 28, 2020 6:20 pm

The Erica Synths Pico Quant:

https://www.ericasynths.lv/media/Pico_Q ... nual_E.pdf

Seems to do exactly what i want - but the lack of LCD/or display + up down arrow to pick my own scales...pretty much means i HAVE to use it with a laptop or smartphone if i want to change scales...ffs...soooo close.

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Re: Achieving simple quarter tones in Eurorack

Post by a773 » Sat Feb 29, 2020 12:00 pm

wuff_miggler wrote:
Fri Feb 28, 2020 6:20 pm
i HAVE to use it with a laptop or smartphone if i want to change scales...ffs...soooo close.
That's not how I read it. Sounds like you can need a device to edit scales, but then these are uploaded in one of the eight slots, and can be dialed in from the front panel...

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