The full work from which the tiny example is taken generates both
printed output and MIDI output. The structure of the full work is
something like:
\include "articulate.ly"
stringpart = { [music] }
\book {
% generated printed output
\bookpart {
\score { \stringpart }
\layout { }
}
% using articulate, generate MIDI output
\bookpart {
\score { \unfoldRepeats \articulate \stringpart }
\midi { }
}
}
(When I say "something like" I mean that this is still a
simplification of the structure of the full work, which actually
contains more parts, i.e., multiple staves, multiple voices.)