Re: scheme: troubles adding an octave...

[Carl Sorensen]

Matthew Hanna <mhanna <at> gmail.com> writes:

> 
> As an exercise in learning to write lilypond scheme extensions, I've been
> trying
> to write a music-function that, given an EventChord or SequentialMusic, will
> return the passage in octaves, so c would return <c c,>.  I've run into a
> problem, though.

I think the problem you're having is that you're displaying only part of the
music; the displayMusic is only operating on the chord which is inside the
relative music expression.

If you change your code as follows:

\version "2.10.20"
{{\displayMusic \relative c' {
   <c' c,>
        }
\displayMusic \relative c'' {
   <c c,>
        }}
}

You will then get the music expressions that include the RelativeMusic output:


(make-music
  'RelativeOctaveMusic
  'element
  (make-music
    'SequentialMusic
    'elements
    (list (make-music
            'EventChord
            'elements
            (list (make-music
                    'NoteEvent
                    'duration
                    (ly:make-duration 2 0 1 1)
                    'pitch
                    (ly:make-pitch 1 0 0))
                  (make-music
                    'NoteEvent
                    'duration
                    (ly:make-duration 2 0 1 1)
                    'pitch
                    (ly:make-pitch 0 0 0)))))))
(make-music
  'RelativeOctaveMusic
  'element
  (make-music
    'SequentialMusic
    'elements
    (list (make-music
            'EventChord
            'elements
            (list (make-music
                    'NoteEvent
                    'duration
                    (ly:make-duration 2 0 1 1)
                    'pitch
                    (ly:make-pitch 1 0 0))
                  (make-music
                    'NoteEvent
                    'duration
                    (ly:make-duration 2 0 1 1)
                    'pitch
                    (ly:make-pitch 0 0 0)))))))


And you can see that the pitches are the same in both expressions.  

In your example, you were passing the displayMusic function just <c' c,> and <c
c,>, which are absolute pitches as far as the displayMusic function could tell.

Carl Sorensen