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.
A cantus firmus (CF) is a melody to which one or more contrapuntal parts, or voices, are added. Since this melody is the sine qua non of a satisfying contrapuntal exercise, particular care must be taken to craft it beautifully. The requirements for an effective CF are as follows: The CF 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).
1. The CF begins and ends on the final of the mode (or the tonic of the key).
2. The CF’s penultimate note should be the note a step above the final (the second 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 precept).
5. The range of the CF is generally limited to an octave; this range is occasionally stretched as far as a 10th. Most CFs move within a much smaller range; some are confined to a 6th or even just a 5th above the final or tonic.
6. Only diatonic notes are used. This includes the leading tone in minor keys and modes, but the leading tone should be used sparingly, if at all. The counterpoint may contain a leading tone in the penultimate measure; therefore, the CF can remain entirely diatonic.
7. The traditional CF 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. The melody should be conceived in terms of what can be sung easily by the average musician (example 2).
9. The following melodic intervals are permitted in the CF: 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. No other melodic intervals are to be used.
10. The tritone (A4 or d5) is to be avoided, even when it is outlined through conjunct motion (example 3).
11. The chromatic half step (a half step between two notes with the same letter name) is not used (example 4).
12. Two successive leaps in the same direction are to be avoided, since they suggest an empty space in the line (example 5).
13. Repetition of groups of notes (a), and sequences (b), are to be avoided, since they give the CF an uncharacteristic predictability (example 6).
14. The CF 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), and should not then be repeated, as this would detract from its commanding effect (example 7).
15. There should be a good balance between ascending and descending motion; the CF should possess a pleasing shape and should change direction several times.
As you can see, CFs are highly specialized melodies. While it is much easier to write a counterpoint to a given melody than it is to compose a good CF, it is important to develop a sense of what makes a melody work. Furthermore, your contrapuntal lines, which you will add to CFs, share many characteristics with a CF. This is why we ask you to experiment with writing your own CFs, but you will also have a library of CFs composed by others, to use when you begin to write your contrapuntal lines.
Cantus firmus EXERCISES:
1) What are some basic characteristics of a cantus firmus (CF)? Consider range, steps and skips, modal expression, among other elements.
2) Sing each of the CFs above twice, first on neutral syllables (e.g. “la” or “ta”), and then using note names to practice your alto clef recognition skill (D – F – E – D …)
3) Write your own CFs. one in each of the six modes, remembering to have a unique climax, and to begin and end on the mode’s final or tonic.
4) How does Morley’s second CF differ from the others? Which norms does he contradict?