How can I include ossia without creating a blank space? - lilypond

Question

I am trying to add an ossia staff above the upper staff of a grand
staff. Working from this mailing list post, I have
constructed a minimal example that almost does what I want. The
problem is that the entire score contains a blank space for the ossia
staff, even in systems that have no ossia.
Here is the example (truly, a melodious composition):
\version "2.18.2"
ossia = \new Staff = "ossia" \with {
\remove "Time_signature_engraver"
fontSize = #-2
\override StaffSymbol #'staff-space = #(magstep -2)
\override Clef #'transparent = ##t
\override KeySignature #'stencil = ##f
} {
\key b \major
\override Staff.BarLine #'allow-span-bar = ##f
\stopStaff
s2.*100 % ???
}
treble = \new Staff = "treble" {
\clef treble
\key b \major
\relative c' {
\repeat unfold 10 { b8 cis dis fis dis cis }
b4 dis fis |
b4
<<
{ dis, fis }
\context Staff = "ossia" {
\startStaff \tuplet 3/2 { dis8 b dis } fis4 \stopStaff
}
>> |
b2. |
}
}
bass = \new Staff = "bass" {
\clef bass
\key b \major
\relative c {
\repeat unfold 12 { fis,4 fis4 fis4 | }
b2.
}
}
pianoStaff = \new PianoStaff {
\compressFullBarRests
\time 3/4
<<
\ossia
\treble
\bass
>>
}
\paper {
#(set-paper-size "letter")
indent = 25\mm
short-indent = 5\mm
}
\score {
<< \pianoStaff >>
% This changes nothing:
% \layout { \context { \Staff \RemoveEmptyStaves } }
}
Here is the output (PNG image, 85 KB).
Some interesting things to note:
If I remove the s2.*100 at line 13 (marked % ???), or change the
value to anything smaller than 12, the ossia staff renders
completely incorrectly. It appears below the bass clef, includes the
clef and time signature, and is in the key of C (i.e., the rendered
notes include accidentals). Basically, it looks like it's failed to
notice that the ossia staff exists and has constructed a brand new
one. I suspect that this is because the ossia staff is supposed to
extend past each point where it is used—i.e., when switching staff
contexts, one can go "back in time" but not forward. I don't really
understand this, but I can live with it, as it doesn't seem to have
an intrinsic effect as long as \compressFullBarRests is enabled.
I have included the paper size in the MWE to force consistent
dimensions on different systems.
As I noted in the score, adding \RemoveEmptyStaves does not remove
the empty staves.
My question is: how can I keep the ossia staff rendered as it does in
this example (small and above the treble clef) without adding the
empty space on all previous systems?

Answer 1

\RemoveEmptyStaves is not working because the staves are within a PianoStaff, so you must add \remove "Keep_alive_together_engraver" to the \layout block. Here's a minimal example of a documentation snippet slightly modified:
\version "2.18.2"
\new PianoStaff
<<
\new Staff = "ossia" \with {
\remove "Time_signature_engraver"
\hide Clef
fontSize = #-3
\override StaffSymbol.staff-space = #(magstep -3)
\override StaffSymbol.thickness = #(magstep -3)
} \relative c'' {
R1*3
c4 e8 d c2
}
\new Staff \relative c' {
c4 b c2
e4 f e2
g4 a g2 \break
c4 b c2
g4 a g2
e4 d c2
}
>>
\layout {
\context {
\Staff \RemoveEmptyStaves
\override VerticalAxisGroup.remove-first = ##t
}
\context {
\PianoStaff
\remove "Keep_alive_together_engraver"
}
}
Your example is quite big, not a real MWE. s2.*100 doesn't make any sense to me. I suggest that you submit a smaller example.