\version "2.18.2"

scoreABassoonI = \relative c {
bes8. g16 ees4) \oneVoice r8.\voiceOne  ees16( %12
  des8. ees16 f4 ees8. des16 %13
  }
scoreABassoonII = \relative c {
g8. e16 c4) \oneVoice r8.\voiceTwo  c( %8
  aes'8. g16 f4 e8. f16 %9
}
scoreABassoonIPart = \new Staff \with {
  instrumentName =  \markup\column {"Fag I" "Fag II"}
  shortInstrumentName =  \markup\column {"Fag I" "Fag II"}
  midiInstrument = "bassoon"
} << \new Voice { \voiceOne \clef bass \scoreABassoonI }
     \new Voice { \voiceTwo \clef bass \scoreABassoonII }
>>
\score {
  <<
   \scoreABassoonIPart
  >>
}