By Mark Edmundson, English professor Who hasn't at least once had the feeling of being remade through music? Who is there who doesn't date a new phase in life to hearing this or that symphony or song? I heard it—we say—and everything changed. I heard it, and a gate flew open and I walked through. But does music constantly provide revelation—or does it have some other effects, maybe less desirable? For those of us who teach, the question is especially pressing. Our students tend to spend hours a day plugged into their tunes. Yet, at least in my experience, they are reluctant to talk about music...