Selectively remove some staves consisting only of rests

[Andrew Bernard]

I want to remove some staves containing only rests and yet retain others in my quartet score. [When there is a long solo I want the other parts suppressed, but when just one instrument is at rest I want the empty staff to show in the set of four].

The keepAliveInterface must have something to do with it but my attempts lead nowhere. Here's an MWE where if somebody could show how to suppress one staff with rests but show the other this would set me on the path to enlightenment.

Andrew

%====

\version "2.19.82"

violinOne = {
  \override Staff.VerticalAxisGroup.remove-first = ##t
  \set Staff.keepAliveInterfaces = #'()
  \repeat unfold 8 { c''4 }
  \break
  \unset Staff.keepAliveInterfaces

  \repeat unfold 8 { r4 }
  \break
  \repeat unfold 8 { c''4 }
  \break
  % how can I show this line of rests?
  \repeat unfold 8 { s4 }
  \bar "."
}

violinTwo = {
  \repeat unfold 8 { c'4 }
  \break
  \repeat unfold 8 { c'4 }
  \break
  \repeat unfold 8 { c'4 }
  \break
  \repeat unfold 8 { c'4 }
}

\score {
  <<
    \new Staff {
      \violinOne
    }
    \new Staff {
      \violinTwo
    }
  >>
  \layout {
    \context {
      \Staff
      \RemoveEmptyStaves
    }
  }
}

%====