hello and some questions

[Eduard Drenth]

Dear lilypond developers,

First let me introduce myself: Eduard Drenth, software developer (Java,
XML, http://home.tiscali.nl/drenth/, www.vectorprint.nl) and fond of
music. My eldest son attends violin lessons. His tutor does not have a
computer and writes and draws music lessons for his pupils. He considers
writing books at some stage.  My wife suggested that we pick up some of
the writing work for him using a computer.

It has been a few monts now since we started exploring musical notation
software. Rosegarden, NoteEdit, Harmony, Finale and some more passed by.
We decided to choose lilypond. I liked it from the beginning. Although I
spend a lot of time in finding out the last 20% of how to get the music
the way we want, keep it maintainable, reusable, etc. We use Jedit with
the lilypondtool plugin.

Right now I try to write a function and I end up with a question. The
function:

drawLine = #(define-music-function (parser location uptoNote music)
(integer? music?)
#{
    % get the top and center x of the current note
    
    % get the top and center x of the note which is uptoNote further
    % from the current note
    
    % draw a line using postscript based on the values above

    % the code below works, but how do I use variables in the postscript
    % string
    $music \mark \markup {
       \postscript #"0.1 setlinewidth 0 0 newpath moveto 5 2 lineto 10 0
lineto 0 setgray stroke"
    }

#})

Can anyone give me a hint? Is there documentation available to start
looking when I have questions like these? Should I learn scheme? Should
I learn something else?

Thank you in advance, keep up he great work! When I am more experienced
and keep using lilypond I would also like to contribute.

Regards,

Eduard