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

[Kieren MacMillan]

Hi again!

Tried taking your advice, and building the custom context from scratch. The 
problem, of course, is that I don’t know all the engravers and what they do 
(a.k.a. why they’re needed)… and the documentation doesn’t exactly make 
everything crystal clear in that regard.

So far, I have:

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

\paper {
  line-width = 4\in
  ragged-right = ##f
}

rowrefs = #'(6 8 7 2 3 12 5 4 11 1 10 9)
test = { ef4. <fs' a'>8 g2 r4 <b d''>8 cs' }
testier = { bf4 a4 ~ 8 cs''8 4 d'1 }

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 RowReductionStaff
    \inherit-acceptability RowReductionStaff Staff
    \consists "Axis_group_engraver"
    \consists "Staff_symbol_engraver"
    \consists "Rhythmic_column_engraver"
    \consists "Note_heads_engraver"
    \consists "Note_head_line_engraver"
    \consists "Note_spacing_engraver"
    \consists \RowReduce_engraver
    \override StaffSymbol.line-count = #6
    \defaultchild "Voice"
  }
}

\score {
  <<
    \new Staff { \test }
    \new Staff { \testier }
    \new RowReductionStaff << \test \\ \testier >>
  >>
}
%%%

But clearly that doesn’t Do The Right Thing™. Any guidance would be appreciated.

Thanks,
Kieren.
________________________________

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