\version "2.19.52"

% data section

sampleMelody = \relative c'' {
  b4 c d e |
}

alternativeMelody = \relative c' {
  e4 f g a |
}

% formatting section

singleStaffPart = <<
  \context Staff = "mainStaff" {
    \new Voice {
      \sampleMelody
    }
  }
>>

multiStaffPart = <<
  \context Staff = "mainStaff" {
    \new Voice {
      \sampleMelody
    }
  }

  \context Staff = "tmpStaff" {
    \new Voice {
      \alternativeMelody
    }
  }
>>

main = {
  \singleStaffPart
  \multiStaffPart
  \singleStaffPart
  \multiStaffPart
  \singleStaffPart
}

mainScore = \score {
  \main
  \layout {
  }
}

\book {
  \mainScore
}