There are books and books and books on the subject, but mostly in Welsh. It's all about matching metres and scansions and stuff. Can be very technical. I have yet to work it out.

A lot of the old harp 'airs' are used regularly for the 'alaw' (tune) with the 'cyfalaw' (countertune) being devised by the singer according to the words being sung.

I suppose we should think about running a workshop on it for beginners and non-welsh-speakers...

sian