Sure. ABC is basically like a text file, except that some of the characters command actions that translate to a musical staff and music elements. Fields are established at the top of the file, which give the name, key signature, time-signature and other details. Then the actual music notes begin.
The same musical notes, represented by letters of the alphabet, are given as though you were reading a tune by note-names out loud. To get around octave differences, the shift key (Capital letters) is used. You have already established key in the field area, so you only have to use flats and sharps as accidentals, not in the regular names. Keeps it very simple that way.
Durations are notated by a numeric system which mathematically multiplies or divides the note values, which were established by the field.
ABC is great for single-line melodies, like Irish music and other folk music forms. You can also add chords, very easily with abc. I am less familiar with adding lyrics and haven’t been successful with it.
ABC is great for onscreen viewing. But when it comes time to print out legible good looking music, you have to go through the steps of rendering the file into a Postcript description file. There are several software programs that will make that transition for you, then you can use Acrobat distiller to make a nice looking pdf that you can print and/or share with friends via email.
There are different sets of software depending on your platform, Mac or PC. I use a Mac, so I use Barfly to build and modify existing abc files. Then I drag the file over to ABCforMac to make a postscript, distill with Acrobat then print. If ABCforMac doesn’t work, I use YAPS for the same thing, but its an extremely primitive program.
Hope this helps. If you plan to play a lot of Irish tunes and are not prejudiced against sheet music, ABC is a fantastic way to share and find tunes, AS WELL AS alternate versions of tunes.
And it has reached a point that you can find virtually any tune, except copyrighted ones, on the Internet. Most of the great tunebooks are available now online. Saves money and resources, though it no doubt hurts the publishing companies.
Although the Barfly program will actually play the tune out via MIDI, its not that good of a way to hear a tune. There are problems with triplets and dotted notes, so they don’t always sound exactly right plus the overall problem of correct phrasing. I never use the MIDI feature except when I am transcribing something I heard on a record and I am double checking an accidental , etc.
For swapping tunes, ABC is great. When you ask it to do more, it gets complicated to the point that you want to switch over to a real notation program like Finale.
Hope this helps.