Re: Changing slur behavior

[R. Padraic Springuel]

> On 26 Mar, 2020, at 9:54 AM, Aaron Hill <address@hidden> wrote:
> 
> On 2020-03-26 2:24 am, Kevin Barry wrote:
>> I think the right way to do what you are trying is to write an
>> engraver that listens for slur events and alters the spacing of the
>> music. (I would write one if I could, but I'm not at that level yet.)
> 
> Firstly, know that slurs are not the only way to define melismata.  You can 
> instruct LilyPond to have a single lyric syllable span multiple notes using 
> \melisma and \melismaEnd:
> 
> %%%%
> \version "2.20.0"
> 
> \fixed c' { b4( g a2) | b4\melisma g a2\melismaEnd }
> \addlyrics { one two }
> %%%%
> 
> This does not solve the spacing aspect of the original post, but it shows how 
> you can avoid messing about with slurs.

I’ll have to play with this to see how I like it.  The reason I initially 
wanted to mess with slurs was on the off chance that I later wanted to take the 
chant and turn it into a fully modern

> Assuming you really want to use slurs to adjust spacing, here might be one 
> way to do it:
> 
> …snip...
> 
> The engraver listens for slur-events, injecting a spacing-section-event and 
> adjusting some context properties as needed.  The logic is very simple, and 
> there are no safety checks.  Be warned this likely could fail with more 
> complicated music.
> 
> 
> -- Aaron Hill

Thanks for this Aaron.  After some playing I’ve adapted this to the way I 
usually encode chant (where all notes are basically quarters):

\version "2.19.84"

Slur_spacing_engraver =
#(lambda (context)
 (let ((slur-event-dir #f))
   (define (change-spacing dir)
     (ly:broadcast
       (ly:context-event-source context)
       (ly:make-stream-event
         (ly:make-event-class 'spacing-section-event)
         '(())))
     (let ((score-context (ly:context-find context 'Score)))
       (for-each
         (lambda (args)
           (apply ly:context-pushpop-property
             score-context 'SpacingSpanner
             (if (< 0 dir) (drop-right args 1) args)))
         `((base-shortest-duration ,(ly:make-moment -2))
           (shortest-duration-space 2)
           (spacing-increment 0)))))
   (make-engraver
     ((start-translation-timestep engraver)
       (set! slur-event-dir #f))
     (listeners
       ((slur-event engraver event)
         (let ((dir (ly:event-property event 'span-direction #f)))
           (set! slur-event-dir dir))))
     ((process-music engraver)
       (if (ly:dir? slur-event-dir)
         (change-spacing slur-event-dir))))))


\layout {
    \context {
        \Score
        \override SpacingSpanner.shortest-duration-space = 3
        timing = ##f
    }
    \context {
        \Staff
        \consists \Slur_spacing_engraver
        \remove Time_signature_engraver
        \omit Stem
        \omit Slur
    }
}


music = { 
  a' g'
  a'( g')
  a'( ges')
  a'( g')
  a' g'
}

words = \lyricmode { Some words to go un -- der notes }

\new Staff  
<<
     \new Voice = "mel" { \music }
     \new Lyrics \lyricsto "mel" { \words }
>>

I’ve found a problem: accidentals inside of slurs end up colliding with 
preceding notes.  Is it possible to modify the Slur_spacing_engraver so that it 
doesn’t ignore accidentals and takes them into account when deciding the 
spacing between the notes?

✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝✝
Fr. Samuel, OSB
(R. Padraic Springuel)
St. Anselm’s Abbey
4501 South Dakota Ave, NE
Washington, DC, 20017
202-269-2300
(c) 202-853-7036

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