Re: Bug: Choice of notes provokes unwanted dual staff system

[Simon Albrecht]

Hello Lee,

I don’t know how this works with your actual project, but at least this 
example may be much simplified, by the following measures:
– Remove lots of unnecessary braces. Constructs like \new GrandStaff {} 
or <<>> or \relative c' {} already form only one music expression.
– Don’t create a new Staff for the second section, instead continue to 
use the former top staff and stop the other one.
There actually is a bug at play here, since this prints a spurious clef 
even ‘after’ \stopStaff (technically it’s at the same moment). This must 
be worked around by \RemoveEmptyStaves in the concerned Staff.
(– the \layout block can be left out)

Still, you need to manually beam the quavers just before the \set 
measurePosition.

%%%%%%%%%%%%%%%%%
\version "2.18.2"
\score {
  \new GrandStaff <<
    \new Staff \relative c' {
      g'1 \break
      \set Timing.measurePosition = #(ly:make-moment -1/8)
      e8 |
      a1
    }
    \new Staff \with { \RemoveEmptyStaves }
    % \RemoveEmptyStaves here is a workaround –
    % without it a spurious clef appears
    \relative c' {
      \clef bass
      a2. a8[ a]
      \stopStaff
      % this doesn’t fix the problem
      % \omit Clef
    }
  >>
  \layout { }
}
%%%%%%%%%%%%%%%%

HTH, Simon

On 06.10.2016 19:13, Lee Zipin wrote:
> Here's a trimmed script with some comments.
>
> \version "2.18.2"
> \score {
>
> % Begin with a dual staff system -- intro (treble) and accompanying bass.
>
>    { { << \new GrandStaff { <<
>           \new Staff { \relative c' { g'1 \break } }
>           \new Staff { \relative c'
>           { \clef bass
>              a2  a4 a    % no anomaly with these notes
> %            a2. a8 a   % gets weird with these notes
>           } } >> } >> }
>
> % Continue with a single staff, which begins with a pickup note.
>
>      \new Staff { \relative c'
>      { \set Timing.measurePosition = #(ly:make-moment -1/8) e8 |
>        a1 } } }
>
>    \layout { }
> }
>
> As shown - with the second set of three notes under '\clef bass' commented
> out - I get this:
>
> [image: Inline image 1]
> That's the expected result.  Change the 'a2 a4 a' to 'a2. a8 a' results in
> this:
> [image: Inline image 2]
> That's a dual staff, with the (empty) top (bass clef) continuing (I guess)
> from the previous staff system.  (With actual music it continues for the
> remainder of the piece.)
>
> It doesn't happen (in my testing) if I remove the line specifying the
> pickup note in the lower staff.  And it doesn't happen if I remove the
> \score (and \layout) wrapper (which I need for multiple bookparts).
>
> I get the same results on 2.18.2 and 2.19.40.  (This is on Win7, 64-bit.)
>
> -- Lee
>
>
>
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