Abc code
ABC code is a simple text method of representing music so that it can easily be stored on computers and conveyed by electronic means. Ideally it requires a simple programme to interpret it into usable music notation or some form of audible sound.
There are literally thousands of folk dance tunes (as well as other tune forms) on the internet.
The first place to seek information on the abc format is at the abc notation page run by the inventor, Chris Walshaw.
A quick way of getting a tune out of an abc file is to cut and paste the code into the interpreter at Concertina.net
This page will be expanded as necessary but there's enough here to get you started.