These two sites are useful for finding musichttp://www.halcyon.com/aseaberg/ Music Selection Resources on the Web
Seems to be set up for music librarians to track down accurate bibliographic information for cataloguing music in different formats, but there are links to other sites as well
http://celtic.stanford.edu/tunes.html Tunes at Ceolas
this site has a huge database of songs with reference to specific music books where they can be found (look up the name of the book in their bibliography index).
I really wonder whether setting up a songbook index in DT is duplicating other efforts already available on the net, and our time and resources might be better spent in the short term by doing some systematic web searches, finding out what is already available, setting up a links page, and then finding out what the gaps in the information are, and then we could take it from there.
Helen