Combining multiple \tags?

[Panteck]

I've got three sets of tags ( letter/a4/bigprint, part/score, and 
original/edit ).  What I want to do is something like \keepWithTag #'letter 
#'part #'edit, but \keepWithTag doesn't take multiple values, and 
\keepWithTag #'value1{ \keepWithTag #'value2 } doesn't work, because the 
inner \keep strips out all the other tags.

Has anyone else ever attempted to do something like this?  Is there a better 
way of doing what I'm after?

Thanks!

--Steven