De Mensurabili Musica

De Mensurabili Musica (concerning measured music) is a musical treatise from the early 13th century (medieval period, c. 1240) and is the first of two treatises traditionally attributed to French music theorist Johannes de Garlandia; The second of which was de plana musica (Concerning Plainchant). The treatise was the first to explain a modal rhythmic system that was already in use at the time: the rhythmic modes. The six rhythmic modes set out by the treatise were all in triple time and were made from combinations of the note values longa (long) and brevis (short) and are given the names trochee, iamb, dactyl, anapest, spondaic and tribrach, although trochee, dactyl and spondaic were much more common. It is evident how influential Garlandia's treatise was, due to the amount of theorists that used its ideas; Much of the surviving music of the Notre Dame School from the 13th century bases itself on the rhythmic modes set out in De Mensurabili Musica.