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

Tom Wiltshire tom at electricdruid.net
Sun Jul 4 23:42:25 CEST 2021


Hi J-P,

I’d take a programmer’s approach, since that’s what you’ll be doing!

How is the incoming pitch to be represented? I usually use a 16-bit variable where 15 bits are used. The top byte is a MIDI note from 0-127 (hence the missing bit) and the lower byte provides a sub-semitone position of 0-255 steps (so better than half a cent accuracy).

I would build tables giving boundaries for each scale, which the boundaries being specified as 16-bit pitch values. For each boundary, an output pitch would be speciifed (again, to 16-bit accuracy). Then the quantization would become a question of selecting a table, taking an input value, and finding the matching output value by going through to find which boundaries it is between.

This would allow arbitrary scales to be generated, including microtonal things and other unusual stuff, but also give you flexibility to limit things to pentatonics or triads or whatever else.

HTH,
Tom

==================
       Electric Druid
Synth & Stompbox DIY
==================



> On 4 Jul 2021, at 19:43, Florian Anwander <fanwander at mnet-online.de> wrote:
> 
> Hello Jean-Pierre,
> 
> I would take a more musical approach. Always convert the incoming information to the semitone scale, and then transform to the final scale using a list with definitions like that (pentatonic example):
> C-->C
> Cb->C
> D-->Db
> Eb->Eb
> E-->F
> F-->F
> Gb->G
> G-->G
> Ab->G
> A-->Bb
> Bb->Bb
> B-->Bb
> Whether you shift up or down may even depend on the (assumed) base note of the scale. Eg. If you think this as pentatonic over c-minor, then the E is shifted up to F. If you think this a pentatonic scale over Eb-major, the E gets shifted down to Eb. 
> (This is what I am working on at the moment for the quantized transposition of my midi-stepsequencer http://www.florian-anwander.de/sq-3p/ <http://www.florian-anwander.de/sq-3p/>)
> 
> Florian
> 
> 
> Am 04.07.21 um 19:35 schrieb Jean-Pierre Desrochers:
>> 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: 
>> TRIAD C-E-G-C
>> 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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