Pianist David Lanz has been interviewed on the topic: The Spiritual Significance Of Music. He says that:

Music, like spirit, is invisible. Yet it moves us to sing, dance, laugh, cry, even march to war, to heal, and pray, Music has the power to bring thousands of people together to celebrate. What else in life has this power? Everything on this Earth eventually crumbles and returns to the dust of which it was made. Only Spirit remains. Great music endures centuries, outliving its creators and performers.

Read it all here. It is really inspirational.