Re: in a \GrandStaff the order of a staff group and a staff can be inversed

[Keith OHara]

Eluze <eluzew <at> gmail.com> writes:
> 
> with the code 
> 
> \new GrandStaff <<
>   \new StaffGroup <<
>     \new Staff { c'1 }
>     \new Staff { d'1 }
>   >>
>   \new Staff { \set Staff.instrumentName = last f'1 }
> >>
> 
> the staff named "last" is engraved /above/ the StaffGroup

because the StaffGroup is not accepted by a GrandStaff, 
so is pushed out the bottom, while the Staff is accepted
in the Staff Group.

Here we want GrandStaff \with { \accepts StaffGroup } <<>> 
and this would be a better example for Notation Reference 5.1.7
http://code.google.com/p/lilypond/issues/detail?id=3641

I re-opened that issue for documentation because that gives some
context for why 'acceptance' is not universal.  The people working
on the code make implicit assumptions that something like a Voice will 
not contain Staff, and the output is often strange if the assumptions
are violated.