[LAD] Quantise MIDI note/frequency to musical scale: algorithm?

[Jeanette C.]

Thanks Roman. For the actual pitch quantisation I used a similar approach in 
the end. Though for the MIDI case I stuck with the temporary 128 element 
array. Though this is simply calculated from the same set of 12 element 
arrays.

Best wishes,

Jeanette

Jan 1 2022, Roman Sommer has written:

> Hi Jeanette,
>
> If you want to reduce the amount of table elements, you could calculate
> the offset from the key base note, take it mod 12 and have a 12-element
> array for every scale you want to implement (pseudo-C ahead):
>
>      bool minor[] = [true, false, true, true, false, true, false, true,
>      true, false, true, false];
>      uint32_t offset = 2; // key: D
>      // add offset instead of subtract to ensure the result is positive
>      uint32_t additive_offset = 12 - offset
>      uint32_t index = (note + additive_offset) % 12;
>
>      if minor[index]
>         play_note(note);
>
> Won't probably make much of a difference in performance really, but it
> should make it easier to implement all scales in all keys.
> Hope that helps! :)
>
> keep grooving
>
> Roman
>
> "Jeanette C." <julien at mail.upb.de> writes:
>
>> Gopod morning Fons!
>> Dec 31 2021, Fons Adriaensen has written:
>> ...
>>> There is code doing this [quantise frequency to scale] in zita-at1 (the autotuner). It has some
>>> refinements such as an optional preference for the previous note.
>>> I will look this up and isolate it - it may be difficult to find
>>> as it is integrated with other functionality.
>> Many thanks, this is great! You are, as always, very kind.
>>
>> Best wishes,
>>
>> Jeanette
>>>
>>> Ciao,
>>>
>>> --
>>> FA
>>>
>>>
>>>
>>
>> --
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>>
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