conditional

[Aaron]

HI all,
i was wondering if there was a way to make some lilypond markup
conditional.

I mean that in my files I add for example header information that I
don't want to appear in scenero a but for scenero b yes.

Or a music part I want to be in a printout for one person but not for
another.

What I am trying to do is make a hebrew and an english header and be
able to only print hebrew for hebrew and english for english.
Also I want a way to correlate the lilypond header with mp3 headers so
that is I have a recording of the song I notate the header of the
lilypond file will be used to make the header of the mp3 only the header
field names themselves will be different.

ie. title in ly will become track in the mp3 header.
I would need to use a bunch of lilypond header fields only for this
purpose ie my songs have no opus but I may use opus in the header for a
field in the mp3. Is there a way to make these fields conditional???
Thanks
Aaron