If you want to know more about ABC in general, here are some good starting points :-
Chris Walshaw's ABC Pages, which includes huge lists of other tune collections, links to relevant software, and much more. Chris was the original inventor of ABC.
John Chambers' ABC Tune Finder The tunes' search engine. If you're looking for notation of a particular tune, this is where to look. His ABC Music Page is another collection of useful pointers.
Guido Gonzato's ABC Plus project - links and documentation. His Making Music with ABC 2 is the best single piece of documentation that I know of, highly recommended. It mainly refers to abcm2ps, but much of what it says is applicable to the other ABC programs too.
the ABC standard. The ABC uploaded here doesn't necessarily conform to this standard.
The work of turning the material here into useful things is done by various other programs. These all have their own commands and magic words that can be included in the file.
abcm2ps is the site's favourite (default) typesetter for PDFs, both for tunes and for documents.
abcm2ps supports a large number of ABC "directives". These are lines of the form
which affect the display and formatting of tunes and documents.
abc2mtex can also be used to typeset both tunes & documents.
This is the original implementation, ABC according to its inventor, the program that made ABC into a Thing. It is also, by now, very old, and hasn't kept up with subsequent developments, with the result that it has problems with a lot of now-common ABC usages. This probably makes it only of interest to people who have a particular need for it and, hopefully, know what they're doing. Also, it's based on TeX, an ancient typesetting language, which is probably also of interest mainly to those who are already familiar with it. Given that, it's capable of much more sophisticated typesetting than abcm2ps. abc.txt is a brief description of ABC as understood by abc2mtex, and usrguide.ps is an expanded version of the same. These are the original descriptions of ABC, from which everything else proliferated.
Documents can also be typeset by latex.
Yet another typesetter. This is not capable of rendering tunes, but is A Good Thing for documents, because it can generate proper tables of contents (whose entries are links to the relevant item, if your PDF viewer supports them). Also, like abc2mtex, capable of doing extrememly sophisticated stuff, if you know how to tell it to.
For midi, the only option is abc2midi.
Generates midi a file for a tune (you can't do midi for a document). abcguide.txt is a description of how abc2midi interprets ABC including many '%%MIDI' directives to control the output in various ways.
If you were thinking of submitting some tunes, or are just interested, here are some details about how the site works.
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