Hi, I've made some music which I think could be used in Widelands. The music is in a medieval, somewhat Roman style. The music is hosted on LastFM: http://www.last.fm/music/Joshua+O%27Leary/Compositions/From+Scotland+to+Rome I have also made a more open source friendly ogg: http://www.2shared.com/audio/uRzCuA_K/from_scotland_to_rome.html
If you want the source files I have made them available here:
The ogg version would probably sound best because it has been set up for my keyboard's internal sound bank.