\set Staff.midiInstrument = #"contrabass" \melody
\set Staff.midiInstrument = #"tremolo strings" \melody
\set Staff.midiInstrument = #"pizzicato strings" \melody
\set Staff.midiInstrument = #"contrabass" \melody
\set Staff.midiInstrument = #"tremolo strings" \melody
\set Staff.midiInstrument = #"pizzicato strings" \melody