Many moons ago I came across:
Which has lots of data on authors, books and composers (the guy seems to be transcribing a large amount of the US copyright register by hand!).
In the light of our work on the db I wrote to the owner of the site at the start of May and, to my slight surprise, got an immediate response (email addresses on websites are usually dead due to spam). Philip Harper who runs the site was extremely helpful and while not able to make available the general author data as he is planning a semi-commercial collaboration with it he was happy to provide us his composer list as public domain data. I have now posted this up here:
Details of the License for the Data
From Philip Harper’s email:
Rufus Pollock wrote
Also, just for clarity what license would you make available under? (Public Domain, CC Attribution, etc)
It’s so small, and by the time you get anywhere worthwhile it’ll be so small a component, that it’s not worth making any reservations, so straight Public Domain – do whatever you like with it, without attribution or other conditions, and if you can make money out of it, good luck!