My son has just discovered Google Book Search and passed on these links to me. He was quite right that I would find Google Book Search very useful and a search in the Mudcat archive tells me that there is no reference to it yet in the Forum and so I am passing his links on. What Google Book Search does is make books with expired copyright accessible on line and this link explains this more fully and explains how to make use of it

HOW IT WORKS

This link is a search that should be interesting to many of us on Mudcat

Sample Search for Folk song English 0-1922