Re: slurs and ties

[Kieren MacMillan]

Hi Erik,

> As I see it you create the two voices as if nothing special was  
> needed.
> Then create a third voice, with identical notes as the second voice.
> These remain hidden, but the ties are visible.
> Am I correct?

Essentially, with one [very small] correction: the third Voice  
context doesn't usually/always have "identical notes as the second  
voice"... For example, in the first bar of your snippet, we have
      \new Voice { \voiceTwo d,4 <d fs> }
      \new Voice { \tieVoice d8 _~ fs _~ <d fs>4 }
which clearly aren't "identical notes".

The problem is ties that [visually] cross Voice contexts — Lilypond  
can't [yet?] handle that. So my solution is
   1. If a tie [visually] joins two notes within the same Voice  
context, engrave as normal.
   2. If a tie [visually] joins two notes across different Voice  
contexts, create a third Voice context containing [invisible copies  
of] the notes that require joining, and tie them instead.

The other tweaks (e.g., \shiftOff) are there to make sure that the  
regular note collision algorithms don't kick in and misalign/offset  
the "tie Voice elements" (i.e., the ties themselves, plus the hidden  
notes).

Makes sense?
Kieren.