Dewey Music is a search engine and an interface for Archive.org. Archive.org is some kind of an internet archive for free public domain content, which may be accessed for non commercial and private purposes. The archive contains historic documents and documentaries as well as films and music recordings. Dewey Music enables the comfortable access to the above 1 million music pieces by above 10000 artists. Find out more at Dewey Music.

The Archive.org by the way is also archiving different versions of websites in a chronological manner. Too, traexs.com is included with the different versions being available here. And for instance this is the way eBay has started.

Similar services are available at music search engines and music downloads.