Thankyou all for your valuable inputs. The variety of responses and infromation has certainly made me want to find out about this facinating subject and with the information gained now have a good start.

It is fascinating to me to hear about such a fascinating way of getting songs around, and meeting the demands of singers so long ago.
Great response and I certainly would agree that a newcomers dictionary would be a mosr useful link to have- even for use by those that are not such newcomers and are seeking confirmation of their own definition or wanting to challenge or add to existing ones.
Kipling