\score {
      \context Staff = guitar < 
        \global 
        \context Voice=melody { \melody }
        \context Voice=bass   { \bass   }
      >
  \paper {
        linewidth = 18.0 \cm;
        gourlay_maxmeasures =8.;
	\translator { \BarNumberingStaffContext }
  }
}
\score {
      \context Staff = guitar < 
        \midi_stuff
	\global 
        \melody
        \bass
      >
  \midi {
    \tempo 4=160;
  }
}