Cantus Firmus

Josephus: I come to you, venerable master, in order to be introduced to the rules and principles of music. Fux, Gradus ad Parnassum (1725), 19.

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A cantus firmus is a melody to which one or more contrapuntal parts are added. Since this melody is the sine qua non of a satisfying contrapuntal exercise, particular care must be taken to craft it beautifully. Here are the requirements for an effective cantus firmus:

 

 

1. The cantus firmus is traditionally written in alto clef, a member of the movable clef family known as "C" clefs. C clefs include the alto clef, the tenor clef (both still in use today), and the soprano clef. In all C clefs, middle C is located where the arms of the clef meet (example 1).

 

Example 1: the C clefs 

2. The cantus firmus begins and ends on the tonic of the key or the final of the mode. The penultimate note should be the note a step above the tonic or final (the second tonal or modal degree).

 

 

3. All notes are of equal length; the whole note is the traditional value.

 

 

4. Notes are usually not repeated immediately (although, in treatises of the 16th and 17th centuries, examples can be found which contradict this).

 

 

5. The range of the melody is generally limited to an octave. This range is occasionally stretched as far as a 10th. Most cantus firmi move within a much smaller range; some are confined to a 6th or even just a 5th above the tonic.

 

 

6. Only diatonic notes are used in the cantus firmus.

 

 

7. The melody consists of from eight to thirteen notes.

 

 

8. Conjunct (stepwise) movement should predominate, interspersed by three or four judiciously employed leaps.

If the leap is greater than a 3rd, it must be followed immediately by motion, preferably by step, in the opposite direction to that of the leap. This opposite conjunct motion is called "recovering the leap."

 

 

9. The melody should be conceived in terms of what can be sung easily by the average musician (example 2).

 

Example 2: a singable line 

10. The following melodic intervals are permitted in the cantus firmus: major and minor 2nds, major and minor 3rds, perfect 4ths, perfect 5ths, minor 6ths (ascending only), and perfect 8ves.

There is some difference of opinion in the modern literature about the admissability of ascending major 6ths --this is largely a matter of taste and will be left to your own discretion.

All other melodic intervals are forbidden. The tritone (A4 or d5) is to be avoided, even when it is outlined through conjunct motion (example 3).

The chromatic half step (a half step between two notes with the same letter name) is not used (example 4).

 

 

 

 

Example 3: outlining a tritone 

 

Example 4: chromatic half-step 

11. Two successive leaps in the same direction are to be avoided, since they suggest an empty space in the line (example 5).

 

Example 5: two leaps in a row 

12. Repetition of groups of notes (a), and sequences (b), are generally forbidden (example 6).

 

Example 6: note groups and sequences 

13. The cantus firmus should have a climax on a high note, which should be melodically consonant with the first and final notes (i.e. at a distance of a major or minor 3rd, perfect 4th or 5th, major or minor 6th, perfect 8ve, or major or minor 10th). Do not repeat this climactic note, since this detracts from its commanding effect (example 7).

 

Example 7: climax 

14. There should be a good balance between ascending and descending motion; the cantus firmus should possess a pleasing shape and should change direction several times.

 

 

As you can see, cantus firmi are highly specialized melodies. While it is easier to write a counterpoint to a given melody than it is to compose a good cantus firmus, it is important to develop a sense of what makes a melody work. Furthermore, your contrapuntal lines, which you will add to cantus firmi, share many characteristics with a cantus firmus. Therefore, you will experiment with writing your own cantus firmi, but you will also have a library of cantus firmi composed by others, to use when you begin to write your contrapuntal lines.

 

Cantus firmi

EXERCISES

 

You will need manuscript paper to complete these exercises.

 

1. What are some basic characteristics of a cantus firmus? Consider range, steps and skips, modal expression, among other elements.

2. With these basic characteristics in mind, write your own cantus firmus in each of the six modes, remembering to have a unique climax, and to begin and end on the mode's final or tonic.

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Copyright © 2001 Irene Girton