Comment 5 for bug 791025

Turn at least the copy files to folders option off. It is why you are getting duplicates.

I'd recommend turning the others off as well if you don't want your music to be re-uploaded every time you listen to the songs. If banshee is writing data into the files, then they are being changed, and will be uploaded back to the server, and re-downloaded on any other computers you have which also synchronize your music.