How can I get good layout and good midi without writing everything twice?

[Helge Hafting]

I know that a simple melody is easy, just use layout{} and \midi{} to 
get both. It is not always that easy though.

I am typing some traditional folk music into lilypond. In the original 
manuscript, grace notes is used to specify how some pralls are to be 
played. After a few of these constructs, a prall symbol (black zigzag 
line above the staff) is used instead.

This saves space. And according to a musician friend, it makes life 
easier for the musician too. If grace notes were used all the way, the 
musician would have to read closely in case there were any subtle 
differences along the way. But using trill symbols, the musician
knows to play every trill the same way.

Now the problem: I can reproduce the look, and get nice sheet music. But 
I am not much of a musician myself, so I listen to the midi. But 
lilyponds midi output does not interpret a prall as "play the same 
sequence of grace notes as last time".

If I write the grace notes every time, the sheet music does not look so 
good. I could write the piece twice - once for print and once for midi. 
Cut & paste means it won't be that much work initially. But then the two 
pieces could get out of sync, with errors corrected in one and not the 
other.

What I need, is to get the midi output for
 \appoggiatura{e16 fis} e16
but the layout for
  e16\prall

Is there a way to achieve this? Without having two copies
of all the notes?



The original can be found at the Petrucci Music Library
http://imslp.org/wiki/Special:ImagefromIndex/63468
page 3.

Helge Hafting