ABC is a tune notation format. It's mostly intended for modern, Western music, i.e. 12 semitones/octave, bars, time-signatures, etc. Chris Walshaw's abc page is a good place to start, with an explanation of the format and links to software, tune collections and ABC-specific search engines such as JC's ABC tune finder.
One of the points of ABC, for me, is that it uses source files that are human-readable, platform-independent and in a widely-publicised format. This means that you can edit them with your favourite editor (i.e. GNU Emacs) and usefully exchange them with people on alien machines via email. It also means that instead of relying on proprietary packages lots of people can write helpful programs that the system's inventor didn't have time for or hadn't thought of.
I use the following packages - these are free, although some are still licensed:
There are many other packages available: see the abc page for a list.
This page is maintained by Thomas Bending,
and was last modified on 17 May 2021.
Comments, criticisms and suggestions are welcome. Copyright © Thomas Bending 2021