Center for the History of Music Theory and Literature
Explore the history of music theory by learning from the Greek and Latin classics. You have access to a library of Latin-translated analyses of music in addition to previous Italian tracts from the Renaissance. This is a wonderful site for delving into classic music theory.
Introduction to Musical Tuning
In order to get a greater appreciation for music theory you ought to start from the classics. This site takes up the debate about the differences in tonalities in the past and the present. In this online music essay, the author attempts to answer questions on how music was tuned in the days of early music and what we are missing in our translations of the classics.