Want to start a war? Try to work out an authoritative definition for this all too common term, "Christian music." Nearly two decades after Amy Grant recorded "Baby, Baby," Christians can still work up a lather in the culture wars, and worship wars, linked to popular music. Nationally syndicated columnist Terry Mattingly has been covering these battles since his days as a rock columnist in the late 1970s and remains convinced that these debates offer the most revealing window into the heart of Christian niche culture. Prepare to argue with him.