Handling transpositions gracefully

[Mark Probert]

Hi.

I'm not quite sure how to ask this, so please bear with me. Right now 
I'm having fun doing jazz lead sheets (for which lilypond is a 
fantastic tool--lilyjazz is fantastic! thank you!). What I find I'm 
doing is creating a "concert" version, then making a bes version, then 
a ees version (I play alto sax and cornet). Basically all the same 
source except with a \transpose wrapper around the score.

Is there a recommended way of having a single source and then 
triggering the multiple variant outputs? Or do I simply put the stuff 
that remains constant an include and have three separate shells for the 
different tranpositions?

Any thoughts? (I imagine this is a solved problem...)

Thanks 
 ..mark.