If the music you want to listen to is already organized well you can always make playlists with Play, http://sbooth.org/Play/, drop the folders on a playlist window, set it to Repeat All, and rock on. This can help me concentrate: I don't need to star any music, nor check how many plays a song has and whether it will knock another out of my Top 25 list, and I don't get tempted to start mix and matching across genres, thereby distracting from work. I simply put all my Van (as in Morrison, not Halen), or Smashing Pumpkins, or Smiths, etc, into a play list and work.