File include structure complication

[Michael J. O'Donnell]

This is both a warning and a fishing expedition for ideas that I might
have missed.

I am trying to use a style in which I define lots of individual numbers
as bookparts, sometimes produce them separately, sometimes combine them
(often with a choice of several variants for each number) into one book.

It seemed sensible to have a *-score.ly file for each number, with an
outer \bookpart context, and another *-score.ly file for the collection,
with an outer \book context, including each of the bookpart files.

I also like to separate *-music.ly files, containing variable
definitions with notes, dynamics, articulation, *-header.ly files with
\header{ ... } declarations, so that the *-score.ly files just combine
these in a particular desired way (I can vary, e.g., the use of a
4-staff choral S-A-T-B score vs. a 2-staff score with women and men on
the two staves).

Alas, some of the \includes need to go into nonoutermost contexts (e.g.,
to put \header declarations inside the \bookpart contexts, to put the
\bookparts inside the \book), and the variable definitions are
syntactically wrong when they end up inside.

At first glance, it looks like a sensible reorganization where each *.ly
file is either outermost, with only variable definitions, or
nonoutermost, with no variable definitions, will approximately double
the number of files.

Perhaps someone has cooked up a structure for complicated intersecting
books/bookparts that avoids my problems.

Or, perhaps I missed a way to have a variable definition always executed
outermost, even if it appears syntactically inside a \bookpart or other
context.

Cheers,

Mike O'Donnell