Hi, A frequent complaint on this list is the lack of available documentation about LilyPond's inner workings and programming interfaces.
Indeed, I have myself experienced the thorny path to getting a grasp of how to extend LilyPond in Scheme. To remedy this, pushed by Jacques, I wrote up the start of something that could someday resemble an introduction to extending and a guide covering programming topics. It is a work-in-progress and pretty incomplete at the moment. Nevertheless, it contains some unique material, like the explanations about Scheme engravers (totally undocumented). On the long-term, this might make its way into the official documentation in an adapted form. It's here: https://extending-lilypond.readthedocs.io/ I'll be glad if this is useful to someone. I would also appreciate any comments you might have. Regards, Jean
