Multiple score scenario

[Jon Arnold]

Hi -

I think I have a unique scenario and am trying to figure out the best way 
to move forward.

I am working on an edition of Bach's Jesu Meine Freude, and will be doing 
at least three different editions:

1) choral scores of individual mvts
2) book of choral scores
3) book of string parts which double voices (soprano=vln, tenor=vla, etc.)

I have each movement in a file (jesu1.ly, jesu2.ly) and have the staff 
layout stored in a variable so that I can call it on the individual 
movement and the book without getting voice variables confused between 
movements.

So, my book file looks like this: 

\include "jesu1.ly"
\include "jesu2.ly"

\book {
  \score {
    \jesuOneScore
    \header { piece = "Mvt. I" }
    \layout { }
  }
  %etc. etc.

The problem is the instrumental parts. How can I call one voice from one 
particular file? I tried putting the \include command in each bookpart, but 
that tries to pull the whole score for some reason.

The only solution that I can think of is to name each voice and lyric 
variable with a movement (sopranoNotesOne, sopranoLyricsOne), but I'm 
hoping there is a more logical solution.

Thanks so much for any help!

Jon