PianoStaff names

[Edward Neeman]

Hi all,
When PianoStaves are hidden in a system, the
Instrument names seem to behave in weird ways.  In the
following example the PianoStaff.instrument titles are
superimposed on each other, and the PianoStaff.instr
titles both appear even where there is only one
PianoStaff visible.  I've tried it in 2.6.3 and
2.7.12. Haven't figured out a workaround.

Cheers,
Edward Neeman

\version "2.6.3"


PianoIa = \relative c' {

c1 \break c1 \break c1

}

PianoIb = \relative c' {

c1 c1 c1
        
        
}
PianoIIa = \relative c' {
R1 c1
}

PianoIIb = \relative c' {
R1 c1
}
\score {
        
<<
\override Score.RemoveEmptyVerticalGroup
#'remove-first = ##t
\override Score.InstrumentName #'space-alist =
#'((left-edge extra-space . 2.0))
\context PianoStaff = "I" { <<
\set PianoStaff.instrument = "one"
\set PianoStaff.instr = "two"
\context Staff=PianoIa \PianoIa
\context Staff= PianoIb \PianoIb
>>
}
\context PianoStaff = "II" { <<
\set PianoStaff.instrument = "three"
\set PianoStaff.instr = "four"
\context Staff=PianoIa \PianoIIa
\context Staff= PianoIb \PianoIIb
>>
}
>>
\layout { \context { \RemoveEmptyStaffContext } }
}


                
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