There is support in LilyPond for doing it with two parts, see
8.3.1 Automatic part combining. However, it doesn't work for three
parts (actually there are many situations where it doesn't
work that well for two parts either).
However, you can always just put them as three parallel lines in the
greetings!
i am copying an orchestral score in which there are three flute parts,
always in rhythmic unison. we would like them to appear in the full
score as chords, but still be easily extracted for parts. is there a way
(other than a lot of cut'n'paste) to do this?
my basic strategy for t