adding new musical signs

[LEGRAND Jean-Marc]

Hi everybody !

I'm trying to copy with Lilypond somme ancient music (Pieces for the viol by 
Marin MARAIS), and I
have to use somme specific musical marks, such as horizontal and vertical 
tremolos, cross before a
note, and left oriented stems. Is it possible to create marks and use them in 
Lilypond ?

Another question : is anybody familiar with baroque music edition with Lilypond 
?

Best regards