II Tonus Plagalis, Imperfectus Mixtus Imperfectus, Commixtus Imperfectus Mixtus with the VII
The Source of this Chant from the Gregorian repertoire
This is a II Tonus Imperfectus Mixtus Imperfectus with the Commixtio Imperfecta Mixta with the VII Tonus!
October 4th is the Feast of Saint Francis of Assisi, and the Catholic Church celebrates the commemoration of the saint with a festive tone.
This important feast is dedicated to an entire Introit in the Graduale de Sanctis, the book containing the Mass chants specific to the Proper of Saints.
While flipping through the Editio Medicea, I came across this very particular chant, which is a II Tonus Imperfectus, Mixtus Imperfectus, with the Commixtio Imperfecta Mixta with the VII Tonus.
But what does all this mean?
Let’s analyze it step by step!
Tonus Perfectus and Imperfectus
A Tonus can be Perfect or Imperfect. In this case, the II Tonus is imperfect because it does not cover the full range of the Diapason of the II Tonus, formed by the first species of the Diapente (La Sol Fa Mi Re) + the first species of the Diatessaron (Sol Fa Mi Re), both descending, since it is a Plagal tone.
Tonus Mixtus
A Tonus can also be Mixtus, meaning it shares the Diatessaron of its companion. And since this is a Plagal Tonus, its companion is the I Tonus Authenticus.
For this reason, the Bfa note that appears in the middle of the chant creates the Imperfect Mixtio with the I Tonus, partially participating in the first species of the Diatessaron (Dre Emi Ffa Gsol).
Tonus Commixtuse
A Tonus can also be Commixtus, meaning it may contain species typical of another Tonus.
In this chant, the presence of two ascending species of the Diatessaron (first species, Re Mi Fa Sol, starting from D and reaching G), and one ascending Diapente of the fourth species (Ut Re Mi Fa Sol), indicate the Commixtio Imperfecta Mixta with the VII Tonus, and not with the VIII, because these are ascending species and not descending.
Video Analysis and Cantus Firmus Course
In this video, we provide a detailed and comprehensive analysis of this chant, allowing you to see firsthand how each of these properties works.
Then, if you want to delve deeper into the subject, sign up for the Cantus Firmus Course to learn how modality functions in Cantus Firmus. This course will teach you to recognize the 8+1 tones of Cantus Firmus, essential for both the traditional and modern Musicus Practicus to navigate the world of Cantus Firmus (monody) and Cantus Figuratus (polyphony).
