Hi Jan- The Ash Grove is an old penillion tune from Wales. It
was played over and over by the harper as the poets would spontaneously
make up and sing verses to it, following very strict and intricate
rules as to where to begin and end singing in relation to the tune.
This is also called "cerdd dant", and I don't know the difference. You
need to contact a Welsh harpist for better info. This art is being
revived in Wales, and I heard it discussed at Welsh Heritage Week in
'83 by Bethan Bryn. She was living at the time in Aberystwyth. Good
luck. Sue Richards