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

[Kieren MacMillan]

Hi Aaron,

> If you permit me to be honest: I would not have the foggiest idea either.  (:

LOL

> The Internals Reference does list which engravers produce which grobs, and 
> there is always the source code itself.  The problem though is knowing what 
> you are looking for.  This is especially tricky when you have normally 
> invisible grobs, since their very existence is a mystery before pulling back 
> the curtain.

Exactly.

> we might need both a custom RowReducedStaff and RowReducedVoice to reach the 
> goal.

Even if that’s not technically required, I think it’s a great idea so I did it. 
Here’s what I have so far, with some "real world" music data:

%%%
\version "2.19.83"
\language "english"

\paper {
  line-width = 6\in
  ragged-right = ##f
  system-system-spacing.padding = #6
}

%%%%%  ↓↓↓↓↓  \INCLUDE  ↓↓↓↓↓  %%%%%
RowReduce_engraver = #(lambda (...)
 `((listeners
     (note-event .
       ,(lambda (engraver event)
         (let* ((elem (ly:event-property event 'music-cause))
                (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))))))))

\layout {
  \context {
    \type "Engraver_group"
    \name RowReductionVoice
    \consists "Note_heads_engraver"
    \consists "Note_spacing_engraver"
    \consists "Rhythmic_column_engraver"
    \consists \RowReduce_engraver
    \override NoteHead.duration-log = #4
  }
  \context {
    \type "Engraver_group"
    \name RowReductionStaff
    \alias Staff
    \inherit-acceptability RowReductionStaff Staff
    \defaultchild "RowReductionVoice"
    \consists "Axis_group_engraver"
    \consists "Staff_symbol_engraver"
    \consists "Bar_engraver"  %%  possibly omit?
    \override StaffSymbol.line-count = #6
  }
}
%%%%%  ↑↑↑↑↑  \INCLUDE  ↑↑↑↑↑  %%%%%

rowrefs = #'(6 8 7 2 3 12 5 4 11 1 10 9)

arco = -\tweak self-alignment-X #RIGHT ^\markup "arco."
pizz = -\tweak self-alignment-X #RIGHT ^\markup "pizz."

global = {
  \time 2/4
  \tweak font-size #2 \tweak padding #2 \tempo "Gemächlich"
  s2*2
  \bar ".|:"
  s2*2 \break
  s2*5 \break
  s2*5
}

vlnI = {
  \clef treble
  r4 cs'\pp\pizz
  d''4 b''
  c''4 af''
  g'4 r
  bf''4\sfp a'
  f''4 fs'
  ds''4\> e'''\!
  r4 c''(\pp^\arco
  b''4-.) d''\pizz
  cs'4 r
  a'4(\f\arco bf''-.)
  g'4( gs''-.)
  e'''4(\> ds''-.)\!
  fs'4\p\> f''\!
}

vlnII = {
  \clef treble
  R2 r4 af'4\pp\pizz
  g4 bf'
  r4 cs''
  d'4\sf r
  b'4\p c'
  r4 ds''\>
  fs'4\pp f''
  r4 a\pp
  bf'4\> g'\!
  af4\sf r
  c''4\f\arco( b-.)
  r4 cs'\>\pizz
  f''4\arco\p(\> fs'->)\!
}

\score {
  <<
    \new StaffGroup <<
      \new Staff << \global \vlnI >>
      \new Staff << \global \vlnII >>
    >>
    \new RowReductionStaff << \vlnI \\ \vlnII >>
  >>
}
%%%

My next question is: How do I "partcombine" properly? For example, I’d like the 
noteheads in the reduction staff to appear arranged in "chords" (e.g., with 
proper shifting), even though the original notes might be of very different 
durations. I feel like even knowing the basic area of the function set to look 
in for this task would reveal a whole new world of how to manipulate Lilypond 
music.

Thanks,
Kieren.

p.s. My first "real-world" problem with all of this Scheme-ing will be to 
assist in taking the partcombine mechanism to the intended/expected goal line. 
So it’s great that I’m already running into the kinds of issues I will be when 
working on that.  =)
________________________________

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