Re: Music to my ears... or rather my heart!
It seems to me the purpose of music in spiritual practice is that it is one means by which we may have profound experience (some call it religious experience). Just as a picture is worth a thousand words, the tones and arrangements of music add far more subtle tones of meaning to a few simple words. Further, this mode of communication touches many more 'receptors' in our mental pantheon than does straightforward text. It touches our emotions, our creativity, it stimulates our memories, and so on. This creates a holistic conception of the message that runs much deeper and broader than mere words can embody. As such, when music is appropriate, it can fulfill many of the spiritual functions of the profound experience.
What is the function of profound experience? In my practice it is to help *internalize* principles, values, and concepts on a more deep and intuitive level. This breaches the line between 'head knowledge' and 'heart knowledge' - the difference between simply agreeing with a value system, and conditioning our character to it. This is, in fact, the best use of all ritual and practice in my view.
If music has been chosen poorly, it can likewise instill unwholesome values and responses more deeply.