[there is probably a thread with a better description but here's what I do...
To hear a tune which is provided in "abc notation"

copy all the text (from the X to the end - no more, no less)
open http://www.mandolintab.net/abcconverter.php 
click the big white box
paste what I copied
click "submit"
click "midi"
then open the download
(I think most modern computers will then play the tune automatically?)]