\score {
  \header {
    title = "Weil ich Jesu Schäflein bin"
    composer = "Melodie: Christian Gregor 1784"
    poet = "Text: Henriette Marie Luise v. Hayn 1778"
  }
  \new ChoirStaff <<
    \set Score.skipBars = ##t
    \new ChordNames {
      \global \germanChords \akkorde
    }
    \new Staff <<
      \new Voice = melodie { \global \oneVoice \melodie }
    >>
    ifdef(`STR_1',`\new Lyrics \lyricsto melodie { \textI }')
    ifdef(`STR_2',`\new Lyrics \lyricsto melodie { \textII }')
    ifdef(`STR_3',`\new Lyrics \lyricsto melodie { \textIII }')
  >>
  \layout {
    indent = #0
  }
}