That bug has been opened on https://launchpad.net/distros/ubuntu/+source/rhythmbox/+bug/37115

"When I try to add "Priscilla Herdman/Forever & Always/09. Priscilla Herdman - Somewhere in Time.flac" or another song on the same album or a song by "Simon & Garfunkel" to a playlist in rhythmbox, it does nothing. I think this is because of the ampersand, because other songs can be added.
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> Thanks for your bug. How do you try to add the song to the playlist? What version of Ubuntu do you use? Is the issue from the filename or the tag from the song?
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I dragged the item in the rhythmbox browser over the playlist's name in the 'Source' box. I'm using dapper (rhythmbox 0.9.3.1-0ubuntu3). I'm not sure if it's the filename or the tags because all of my songs are organized the same way in both (i.e. the filenames are all ~/music/ARTIST/ALBUM/00. ARTIST - TRACK.EXT). I think it's the filename because playlists.xml uses the uri, but that's just a guess.
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> Do you drag it from nautilus or from rhythmbox library to a playlist? Clear descriptions of bugs make the maintainers job easier ...
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sorry, I meant the rhythmbox library"