Re: [Scheme coding] how to turn pitches into music

[Kieren MacMillan]

Hi Aaron,

Thanks for the quick and helpful response!

> Yes.  The list-splicing forms of # and $ are #@ and $@, respectively.

Ah!

> In this case, we are using $@ to take the list of bare pitches and have the 
> parser handle them the same as if the user had simply entered them.

Nice to know how that works.

> I have learned to never make assumptions on performance without concrete, 
> profiling data.

A good philosophy.

> Mainly, I wanted to show you a different coding pattern just so you are aware 
> of the options available.

Definitely appreciated!

> music-pitches extracts just the pitch information from the music.  That means 
> a lot of what makes up a music expression is lost in the process.  For 
> instance, chords will appear as individual pitches.  Depending on your needs, 
> this could be acceptable.

It was also a relatively gentle way in to Scheme-ing.  ;)

> However, is it ultimately your intention to transform a music expression by 
> altering the pitches according to some process (like a \modalTranspose)?

Yes.

> If so, extracting pitches is probably not the best approach.  Instead, you 
> will want to use music-map (or one of its kin) to help you traverse the music 
> expression, so you can then conditionally modify each part as needed.

Very helpful! Here’s an example of what I’m currently playing around with:

%%%%  SNIPPET BEGINS
\version "2.19.83"
\language "english"

rowrefs = #'(6 8 7 2 3 12 5 4 11 1 10 9)
test = { ef4. <fs' a'>8 g2 r4 <b d''>8 cs' }

xform-pitches =
#(define-music-function (music) (ly:music?)
   (music-map
    (lambda (elem)
      (if (memq 'note-event (ly:music-property elem 'types))
          (let* ((pitch (ly:music-property elem 'pitch))
                 (semitone (ly:pitch-semitones pitch))
                 (index (modulo semitone (length rowrefs))))
            (ly:music-set-property! elem 'pitch
              (ly:make-pitch 0 (list-ref rowrefs index) 0))))
      elem)
    music)
   music)

\layout {
  \context {
    \Staff
    \name RowReductionStaff
    \alias Staff
    \inherit-acceptability RowReductionStaff Staff
    \omit Clef
    \omit TimeSignature
    \omit Stem
    \omit Flag
    \omit Beam
    \omit Dots
    \omit Rest
    \omit BarLine
    \override NoteHead.duration-log = #4
  }
}

\score {
  <<
    { \test }
    \new RowReductionStaff { \xform-pitches \test }
  >>
}
%%%%  SNIPPET ENDS

Thanks for your help so far!

Cheers,
Kieren.
________________________________

Kieren MacMillan, composer (he/him/his)
‣ website: www.kierenmacmillan.info
‣ email: address@hidden