transpose definition

[David Bobroff]

I'm trying to figure out how to define a \transpose function.  What I
want to do is to put this definition in a file along with clef
definitions.  I want to do this so the piece can quickly be altered for
different ensembles (i.e. brass choir, trombone choir).  I have a file
with all the instrument names and clefs and I would like to add a
transposition definition so that I can edit this all in one file.  I've
tried several different ways and have not found one that works yet.

I would like to put something like:

\score {
        \notes \myTransposition {...}
}

and have:

myTransposition = <something that works>

in another file.

I've tried to define the whole '\transposition x x' which doesn't work. 
I have also tried defining just the transposition string and using:

\transpose \myTransposition

which also doesn't work.  I get parse errors.  Sometimes they are
'unexpected SCORE' or ' unexpected STRING_IDENTIFIER, expecting PITCH or
NOTENAME_PITCH or TONICNAME_PITCH:'

Is there a way to do this?

-David Bobroff