\version "2.18"
\new PianoStaff <<
\new Staff \relative c' {
\repeat unfold 5 { c4 e g c }
\repeat unfold 12 { c2 a }
\repeat unfold 20 { R1 }
\repeat unfold 10 { c2 a }
\repeat unfold 8 { c,4 e g c }
}
\new Staff \relative c {
\clef bass
\repeat unfold 5 { c4 e g c }
\repeat unfold 42 s1
\repeat unfold 8 { c,4 e g c }
}
>>
\layout {
\context {
% \Staff \RemoveEmptyStaves
}
}
Measure 18-48 should have no lower staff. RemoveEmptyStaves unfortunately doesn't work since the rests shall be printed in at least one staff.