Nicolaus Listenius's "Musica" (1537) proved to be one of the two most successful music textbooks in the Lutheran Latin Schools of the sixteenth century, issued in at least forty-six editions and surviving in use into the next century. Yet, a casual inspection of the book today does not readily yield to modern expectations of a successful pedagogical text; indeed, there has never been any thorough analysis of the book to determine its merits and defects and so the causes of its popularity. The present analysis demonstrates that the "Musica" utilizes a variety of influential practices--medieval, humanist, and Lutheran--combined with an innovative new concept in music pedagogy in order to account for its success. It also reveals certain weaknesses and flaws in the book but argues that these were mostly overcome by the intended practice of guidance from the instructor in actual classroom use. The book's method presents a difficulty for understanding today because of our modern assumptions about proper pedagogy, but an analysis of its method is beneficial for making more conscious those assumptions and advances in current practice.