Unmatched pairs for LilyPond ties and slurs

Question

In LilyPond, ties and slurs are expected to come in matched pairs. I keep coming across situations where a tie or a slur aren't matched. For example:

• As demonstrated in the MWE below, it is possible to have a tied note that goes into a coda (or repeat or some other form of musical jumping) but in LilyPond the ~ form of the tie can't be added to the first note in the coda because it is separated from it's initiating note by line breaks and additional notes
  • It actually surprises me that musical redirections like coda and segno aren't environments like the \repeat volta n {} \alternative{{}{}} setup but that's neither here nor there, I simply bring it up in case I'm wrong and there actually is an environment for coda's and segno notation and jumping.
• I frequently use a lilypond-book compile to produce only one or two bars to include in a document, and I may want an a tie or slur to be implicitly started, but I only care about presenting the bar in question following the tie or slur marking.

I know LilyPond is designed more for typesetting than understanding flow, but can I force LilyPond to print a tie or a slur without having an original note in mind?

    \version "2.18.2"
    {
      \relative c'' \repeat unfold 2 {
          c4 c c c~
        }
        
        % Set coda sign as rehearsal mark and adjust size if needed
        \once \override Score.RehearsalMark.font-size = #4
        \mark \markup { \musicglyph #"scripts.coda" }
        \relative c'' \repeat unfold 2 {
          c4 c c c
        }
    
       \break
    
       \once \override Score.RehearsalMark.extra-offset = #'( -4.5 . 0 )
    
       \once \override Score.RehearsalMark.font-size = #5
       \mark \markup { \musicglyph #"scripts.coda" }
    
       % The coda
       \relative c'' \repeat unfold 5 {
          ~c4 c c c
        }
        \bar"|."
    }

To get this MWE to successfully compile, all that is needed is to remove the ~ in front of the last c4 in the final unfold environment.

Answer 1

Turns out Lilypond has a command to add tied notes that may be unmatched due to codas or repeat signs:

If you follow the tied note that is other wise unable to be connected with the tie-initiator with the command \repeatTie, the tie shows up in the right place.

I thought there would have been a more general environment style solution so while this works for ties, I haven't yet found an equivalent solution for the slurs.

It took me a while to figure out that \repeatTie has to follow, not precede, the note you wish to connect.

\version "2.18.2"
{
  \relative c'' \repeat unfold 2 {
      c4 c c c~
    }

    % Set coda sign as rehearsal mark and adjust size if needed
    \once \override Score.RehearsalMark.font-size = #4
    \mark \markup { \musicglyph #"scripts.coda" }
    \relative c'' \repeat unfold 2 {
      c4 c c c
    }

   \break

   \once \override Score.RehearsalMark.extra-offset = #'( -4.5 . 0 )

   \once \override Score.RehearsalMark.font-size = #5
   \mark \markup { \musicglyph #"scripts.coda" }

   % The coda
   \relative c'' \repeat unfold 5 {
      c4\repeatTie c c c
    }
    \bar"|."
}

Answer 2

The problem here is the \repeat unfold 2 { ... } after the first coda sign.

That does not contain a ~ for "start tie." When it is expanded, Lilypond has finished typesetting its last note, without a tie.

So the in the following ~c4, the ~ has nothing to attach itself to.

One fix is just to remove the \repeat unfold 2 and put the ~ where it belongs:

\relative c'' { c4 c c c | c c c c~ }

   \break
   ...
   % The coda
   \relative c'' \repeat unfold 5 {
      c4 c c c
    }

If you really want to keep the \repeat unfold construct, you can make a parallel passage consisting only of spacer rests, and start the tie from inside that:

    \mark \markup { \musicglyph #"scripts.coda" }
    \relative c'' {
        << \repeat unfold 2 { c4 c c c }
           { s4*7 s4~ }
        >>
    }

   \break
    ...
   % The coda
   \relative c'' \repeat unfold 5 {
      c4 c c c
    }
    \bar"|."

This works because the ~ is "merged" with the notes after the \repeat unfold has been expanded. Incidentally, this is also a good way to attach different dynamic marks, etc, to different repeats of the music in a \repeat unfold.