Adding to what I said below, I think it is important to note that goood music, written by a Christian, will be good music that happens to be Christian. Explicitly Christian art of all kinds has its place, which is why there are hymn writers, and icon painters, and church architects. But what I am referring below to is music intended for popular consumption, music for listening to in the car on the way to the mountains for a weekend of camping, or playing during surgery, or while fixing the car in the garage. Music you play softly while healing a broken heart, loudly while playing volleyball at the beach.
We use music as the soundtrack to our lives, to accentuate emotion, to understand experience deeper, to unify cognition and emotion in the spiritual whole that makes us human. It aids our search for truth. And truth is not painted in the colors of Candyland, it is not always sweet, it is not always pretty. There is great sadness in this world of our destruction, no matter how much beauty waits beyond. And by telling that story, the whole story, of love and loss and pain, an artist shows us ourselves, in a way we cannot.
But I'm reasoning myself into a corner. If music is so deeply affecting, why should it not be explicitly focused what matters most?
I think it has something to do with the reason that every man is not called to be a pastor. For the world to continue, we must have janitors, bus drivers, factory workers, even doctors. We cannot live lives secluded. But does that necessity for interaction require music of the kind I am describing?