How to handle changing transpositions

[Urs Liska]

Hi list,

I have a problem understanding how to efficiently deal with horn parts 
that change their transposition with the clef.

That is: In the treble clef the part is notated as \transpose f, c
while in the bass clef it is notated in concert pitch.

Is there a convenient way in LilyPond (or has somebody come up with a 
solution) for this issue?

As this change regularly happens for just a vew bass notes I wouldn't 
want to wrap each in individual variables.

Any ideas/experiences?

Best
Urs