eTantrum has released its Songprint SDK and created a project here on SourceForge to help coordinate its development.
Songprint is a GPLed library that can automatically identify any piece of music. It does this by determining a song's unique audio "fingerprint", which is based on the its acoustic properties and is independent of the song's method of encoding. Most importantly, it is not in any way dependant on ID3 tags or other information stored in the file itself. If it cannot identify a song, it will give a URL where the song can be added to our database.
Although our song collection is relatively large, there are still many songs out there that we do not have data for. Because of this, not all songs can be identified (yet). However, interested developers can help us complete our database of songs.
You can learn more about us at http://freetantrum.org. Things are still getting sorted out here on our side, so please bear with us as we get all of this organized.
-The Songprint Development Team