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By Andre Madatian
*The image above: “Gregory dictating, from a 10th-century manuscript.” Hartker of Sankt-Gallen.
For those who have studied music history or perhaps have taken a composition class in college — the term “cantus firmus” may be somewhat familiar. For others, this may sound like a made-up term or possibly the name of a new Transformers character…
Regardless of your familiarity with the term, it’s actually a relatively simple concept when analyzing musical excerpts from our past, predominantly from sacred music of the Middle Ages period.
The Middle Ages are regarded as the longest period of music spanning approximately 1,000 years from 450 to 1450, just before the start fo the Renaissance period. “Cantus firmus” is a Latin term that translates to “fixed song” — referring to a pre-existing melody, often times used for plainchant music of the Middle Ages.
Cantus firmi (plural) often underly a polyphonic musical composition, referring to more than one independent voice or part. Some of the greatest and earliest composers utilized cantus firmi, including: Josquin des Prez, Guillame DuFay, and Giovanni Pierluigi da Palestrina (to name a few).
When presented in one voice, the cantus firmus is considered to be called the “vox principalis” or the “principal voice.”
Ex. Cantus firmus (vox principalis)
As music composition advanced and monophony lead to polyphony — the addition of voices were added to the principal voice. In the Middle Ages, when a freely composed melody was added above the principal voice, a new style emerged called “organum.”
Throughout the centuries of music, the cantus firmus was presented from being the top voice to the bottom voice and then ultimately, in the middle voice using the tenor voice. Additional organum voices would then be added above this cantus firmus. Tenor comes from the Latin word meaning “hold.”
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As demonstrated in the “Notre Dame” style of organum made popular by French Middle Age composers Leoninus and Perotinus during the 13th century, the reasoning behind the use of the tenor voice was because notes from the original chant tune were elongated or stretched which is representative of its Latin meaning.
Just like modern times, composers from the Middle Ages composed original melodies, however, composers from this time period often used a notation system that pre-dates our traditional notation system. Composers in future periods of music expanded on the early concepts of cantus firmi to develop the compositional style of “counterpoint” that is still widely used today.
Composers such as J.S. Bach from the Baroque period (1600-1750) took the “rules” and concepts of the cantus firmus to develop more complicated styles of polyphonic composition. The art of composing a cantus firmus was essentially the basis for Western music’s approach to polyphonic writing.
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So now that we know what a cantus firmus is, how do we write one?
Well, like all early composition, there is a very particular set of rules that need to be followed when writing an original cantus firmus. Although these rules were most likely unintentional by the composer during its conception, it is instead through years of reflection and analysis of early music which has led music theorists and historians to intellectualize the process.
Besides the use of the tenor clef, the first musical technique that you might have noticed with the above example is the use of only one rhythmic value: the whole note. Aside from a limited rhythmic range, a proper cantus firmus should also progress in fairly small intervallic movements. It’s also important that the first note of your cantus firmus is also the last note.
As you can see from the above example, the first note is the same note as the last. Typical of a cantus firmus, there should only be one note that is a large intervallic leap and considered to be the “climax” of the melody. This climactic note tends to occur somewhere in between the cantus firmus and usually around three to five measures before the end of the cantus firmus depending on the numbers of measures.
Another rule of writing a proper cantus firmus is to have a balance between stepwise motion and leaps. “Stepwise motion” means that the movement from pitch to pitch is within a whole step above or below.
The above example shows stepwise motion moving up from the note F in measure 1 to G in measure 2 and A in measure 3 (reading in treble clef). An interval larger than a second is considered a leap. Although not as drastic of a leap between measure 7 and 8, there is a leap down of a major third between measure 3 and measure 4 followed by a leap down of a minor third from measure 4 to measure 5.
In proper cantus firmus writing, larger leaps (such as that at measure 8) needs to resolve by moving in an opposite direction. The leap from measure 7 to measure 8 is up a perfect fifth, which is considered a relatively large leap.
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To “balance” the cantus firmus, the melody must then move in an opposite direction. With the above example, measure 8 moves down to the next pitch in measure 9. This opposite direction of movement balances the large intervallic leap between measure 7 and measure 8. If the melody of your cantus firmus moves up an entire octave, the following pitch in the next measure must move down a step. (So for example, D3 up to D4 and then down to C4.)
As a general rule, you do not want your cantus firmus to move in one direction for too long. If you have three or four notes ascending, then it is essential to change the direction of intervallic movement. In addition to the direction of intervals, a composer must also be mindful of particular intervallic pitches to ignore.
For example, since cantus firmi have been utilized as far back as the Middle Ages, the interval of the augmented fourth or “tritone” must be avoided. Since the Middle Ages consisted primarily of a sacred society, the dissonance created by the tritone was considered to be demonic and unworthy of use in composition.
In addition to the tritone, other intervals to avoid include a minor seventh, major seventh, and any interval that is greater than a perfect octave.
And lastly, if you’re interested to learn more about compositional techniques and tools, here’s a history of the oft-misunderstood “△” chord symbol, courtesy of Soundfly’s YouTube channel.
Let’s recap!
Here is a breakdown of rules to consider when composing a cantus firmus:
- Use only one rhythmic value: the whole note.
- Compose using fairly small intervallic movements between pitches.
- The first note of your cantus firmus must also be the last note.
- There should only be one note that is a large intervallic leap and considered to be the “climax” of the melody.
- Must have a balance between stepwise motion and leaps.
- Larger leaps needs to resolve by moving in the opposite direction.
- If the melody of your cantus firmus moves up an entire octave, the following pitch in the next measure must move down a step.
- You do not want your cantus firmus to move in one direction for too long.
- If you have three or four notes ascending, then it is essential to change the direction of intervallic movement.
- Particular intervallic pitches need to be ignored (augmented fourth, minor seventh, major seventh, and any interval that is greater than a perfect octave).
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