...If I could add one thing: Kantors also tend to have theological training, in addition to musical training. As Bach said (and I paraphrase), "A church musician music be a theologian first." In fact, there is a growing trend of kantors being ordained pastors, as well as trained musicians. Both seminaries have one (Kantors Resch and Gerike), as well as church such as Hope Lutheran in St. Louis.
Lest I forget this important distinction! A kantor in the Lutheran Church - Missouri Synod usually studies at an institution of the Concordia University System and/or one of two seminaries. A music class with a theological bend might focus on what liturgy and music teach us about our faith.
To paraphrase Carl Schalk, topics are covered from the perspective of liturgical theology because most dogmatics books don't touch on these things. If they do, it is way in the back of the book, right after The Last Things.
Of course, not all kantors come through the Concordia system. These kantors might attend workshops and lectures sponsored at the local, district, synod or university/seminary level. Another option is a masters program in church music through one of the Concordias.