graphics in scheme?

[Tao Cumplido]

hi,

in this snippet http://lsr.dsi.unimi.it/LSR/Snippet?id=335
stencils are created with commands like make-circle-stencil.
are these part of scheme or of lilypond and is there a list of all possible 
commands available?

also is this similar to the postscript command inside a markup-block and if not 
is it actually possible to use postscript (with variables) inside scheme?

I am a complete scheme newbie and I'd like to create some custom articulations.
I tried it with postscript but then I have to do it every time it appears and 
now I saw the snippet with the snap-pizzicato and thought this could be another 
solution.

regards,

Tao
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