When arranging music I prefer to work with a full score. Once
the arrangement is complete however, building the part specific
learning midis is a tedious process requiring me to rewrite the
file to separate out the music definitions from the score block
and then create a bunch of special files with appropriate names
which input the music definition file by name (so I can't just reuse them -
they have to be edited each time anew) and contain a score block
to construct the desired midi part files. Finally I have to run lilypond on
each of these separately ( a slow repetitive and boring process).