Meditating on music can be a powerful tool for practice. It is a pretty new device actually, because only recently music became predictable. I mean, precisely the same song can be played, and repeated. Human beings have 3 inborn fears, and one of them is fear of noise. Some aspects of our being are kept in continuous stress, to prevent eventual damage caused by sound. If one meditates on sound that is predictable, one can remove this tensions and hear the sound "as it is". This is attained through removing aversion or desire for sound, by repeating the same melody, over and over again.
Sound should be low, and music dynamic and melodic. I don't recommend peaceful "meditation music", because one will fall asleep. No lyrics, and no heavy music like metal, or even rock. Something on the edge of ambient and trance give the best results for me. Just sit, focus on the music, and relax. Sound will become sharp and clear, going deep inside.