\version "2.18.2"

\paper { #(set-paper-size "a7") }
#(set-global-staff-size 14)

\header {
  title = "The Title in external header"
  subtitle = "The Subtitle"
  subsubtitle = "The Subsubtitle"
  poet = "The Poet"
  composer = "The Composer"
  meter = "The Meter"
  opus = "The Opus"
  arranger = "The Arranger"
  instrument = "The Instrument"
  dedication = "The Dedication"
  piece = "The Piece in external header"
  head = "The Head"
  copyright = "The Copyright"
  tagline = "The Tagline"
}

thescore = \score {
  \new Voice { \clef treble s1 }
  \layout { }
}

\pageBreak

\score { \thescore }
\score { \thescore }

\score {
  \thescore
  \header {
    opus = "Newer Opus"
    piece = "Newer Piece in internal header"
  }
}

\score {
  \thescore
  \header {
    piece = "Newest Piece in internal header"
  }
}