Generate special note head shapes
When a note head with a special shape cannot easily be generated with graphic markup, a drawing specification for ly:make-stencil can be used to generate the shape. This snippet gives an example for a parallelogram-shaped note head.
Unfortunately, the available commands in a drawing specification are currently not documented (this is tracked in Issue #6874); in any case, the used path sub-command has the following signature, quite similar to the make-path-stencil Scheme function.
(path thickness command-list line-cap-style line-join-style fill)
The commands in command-list resemble PostScript drawing commands but with arguments after the command name.