Re: [LAD] Quantise MIDI note/frequency to musical scale: algorithm? - Linux-audio-dev

1 Jan 2022

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." &lt;julien(a)mail.upb.de&gt; 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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