Re: Percussion Decorations

[Gilles]

> > Is it possible to "decorate" drum notes?  Such a decoration is meant to 
> > indicate
> > a specific way of hitting the instrument.
> > 
> > For example, after a gong note (represented below with a triangle head), 
> > there 
> > should be a tilde-like "decoration" (to indicate that it must be scratched 
> > with
> > a metallic rod):
> > 
> >   |>~
> >   |
> > 
> 
> Can't anyone help me with this?
> 
> I assume it's done by changing the note head.
> Is there an example in the manual?  Where?

Based on "molecule-hacking.ly" in "Regression Tests", I've come
up with the following:

-------
#(define (scratch-callback callback)
   (define (scratch-stencil grob)
     (let* ((fn (ly:get-default-font grob))
            (dgrace (ly:find-glyph-by-name fn "flags-dgrace"))
            (darrow (ly:find-glyph-by-name fn "scripts-arpeggio-arrow--1"))
            (scratch (ly:stencil-add dgrace
                                     (ly:stencil-translate darrow '(0.95 . 
-0.2))))
            (subject (callback grob)))
       (set! subject
             (ly:stencil-combine-at-edge subject 0 1
                                         (ly:stencil-translate-axis scratch 
-0.8 1)
                                         0.0))
       subject))
   scratch-stencil)
-------

which produces a "twisted" arrow, reminiscent of the path
of the rod on the gong, sort of ;-}

Gilles