Clef change on a Lilypond file ought to be trivial. My understanding is that the notes can be specified either absolute or relative. The clef sign shouldn't alter pitch, so changing it ought to be just a matter of a simple change in the data file.
'tis the case. Did a simple test. Generated a little scrap of music. The lilypond file follows. Changed the "clef treble" to "clef tenor" and "clef tenor" to "clef bass" ... and the notes were correct for the appropriate clef, ie the pitch didn't alter.
If you prefer the "GUI" approach: just change the clef in Denemo using "Clef -> Initial Clef" from the "menu of objects" toolbar. Quite a nice application, this denemo. Have to keep that in mind. :-) Cheers, Peter -- Peter Reutemann, Dept. of Computer Science, University of Waikato, NZ http://www.cs.waikato.ac.nz/~fracpete/ Ph. +64 (7) 858-5174