[sdiy] Quantizer project.. incoming CV's switching point to change to quantized output CV's ...

Richard Wentk richard at wentk.com
Tue Jul 6 15:35:08 CEST 2021

I would ignore microtonal options because they’re impossible to set up and control on a device with a tiny panel, and hardly anyone uses them. 

So you get 12 steps -> oct with hysteresis on input, producing a numeric semitone + octave, through lookup tables which translate semitone + oct into various output scales. 

Don’t forget scales should be transposable. If you have semitone + oct on input that’s easy with a bit of extra arithmetic.

There are actually two kinds of transposition - modal and in-scale. 

You do one before the lookup table and one after.

Quantise -> modal transpose -> scale lookup -> scale root transpose. 

E.g. +n -> lookup to C Major -> +0 -> Various modes of major

You’re moving up and down a note range in the same scale with different lowest (‘root’) notes.

+0 -> lookup to C Major -> +n -> Various major scales

You’re selecting different major scales

Of course you can combine these options too. Voltage control of both separately is *very* useful for complex sequencing.

This looks super-complicated, but if you use C scales only in your lookup you can select different roots/modes with the transpose options. 

So you don’t need separate lookup tables for C major, D major…. C Dorian, D Dorian.. and so on. Just one for each scale type, and a bit of logic to select the transpositions.

This also works for “short” scales like Pentatonic, triads and other chord shapes, and so on.


> On 6 Jul 2021, at 01:07, Jean-Pierre Desrochers <jpdesroc at oricom.ca> wrote:
> This a very good point..
> And the "equal voltage invervals between each note" approach
> seems easier to implement in code using a lookup table with
> a ‘definition’ for each scale..
> This approach will effectively give a scale the same ‘luck to be played’
> for all of its notes. And is less picky on the threshold voltage precision.
> I’ll keep note of this. Thanks !
> De : David G Dixon [mailto:dixon at mail.ubc.ca] 
> Envoyé : 5 juillet 2021 19:43
> À : 'Jean-Pierre Desrochers'; 'SDIY'
> Objet : RE: [sdiy] Quantizer project.. incoming CV's switching point to change to quantized output CV's ...
> I don't know diddly-squat about code, but I've been working on an analog quantizer with logic for generating various scales, and I must say that I'm a strong advocate of the "equal voltage invervals between each note" approach.
> Of course, for the chromatic scale, this is a no-brainer: 83.33 mV per note.  However, if you want to quantize a major triad, I would use 333.33 mV per note.  For a major scale, 142.86 mV per note.  Et cetera.
> Why?  Because if you are running the scales or arpeggios by playing the quantizer with a triangle wave LFO, you will want each note to last for the same amount of time.  Any other approach will impose a rhythm that will favour notes that are farther away in pitch from the others.
> As usual, the right answer is the musical one, not the technical one.
> From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Jean-Pierre Desrochers
> Sent: Sunday, July 04, 2021 10:35 AM
> To: 'SDIY'
> Subject: [sdiy] Quantizer project.. incoming CV's switching point to change to quantized output CV's ...
> [CAUTION: Non-UBC Email]
> I'm starting a CV quantizer design and am wondering
> about the following things:
> Let's assume a normal quantized semi-tone scale:
> All the incoming CV's are quantized to semi-tones like this:
> incoming CV 'around' C, output quantized CV -> C
> incoming CV 'around' C#, output quantized CV -> C#
> incoming CV 'around' D, output quantized CV -> D
> and so on..
> 12 equally spaced output quantized intervals. OK.
> But if the quantized scale output is a TRIAD like
> C-E-G-C-E-G-C, etc... ( 3 quantized intervals)
> where are the switching bounderies of each incoming note CV's 
> to change to the next outputed quantized note ?
> This question is for ascending and/or descending notes..
> Same question for a quantized PENTATONIC major scale output like
> C-D#-F-G-A#-C-D#-F-G-A#-C, etc.. ( 5 quantized intervals)
> I would think of dividing the octave range with 
> equal intervals with the number of intervals
> inside the actual quantized scale..
> For example: 
> That's 3 intervals
> 1 octave = 1 volt
> so 1volt/3 intervals = 0.333v between each quantized notes (??)
> or
> PENTATONIC major scale C-D#-F-G-A#-C
> That's 5 intervals
> 1 octave = 1 volt
> so 1volt/5 intervals = 0.20v between each quantized notes (??)
> But... I don't think that is working this way..
> I think I must keep the incoming CV interval sizes
> and use them for the quantized switch points.. (???)
> Your opinion on that ??
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