yes, the freq. sweeps are great for setting up the sub crossover/phase settings for music listening...
The music selection is pretty good and the booklets they come with actually describe what you should be listening for. Very educational and informative. I actually purchased these discs while I was shopping for speakers a while ago...
I second the recommendation. The frequency sweeps are very useful for drawing your own response curves that are room specific.
The music is VERY well recorded, clean and Keith is right...if you read the manual you will know what to listen for and find out if your system is reproducing things the way it was intended.
I only have one (Test disk 3). I don't think you need all three, I would think it would get redundant after just one, but if you get a economies of scale savings by purchasing all three, why not?