Essential Musicology Reading?

What would you consider to be essential reading for a newcomer to musicology? I took an "Intro to Musicology" course in grad school, but the readings were diffuse, dealing with historiography that wasn't necessarily music-oriented before peppering in some more pointed (but maybe too specific) case studies. I'm wondering if there's a good introductory tome you like to use, or at least some seminal books and papers that make the rest of the discipline make sense.