Lindsay Davidson 
Driving 'piping forward

Cantus Firmus

The cantus firmus is the basic melody on which a polyphonic piece is based.

Originally it could have been anything, from a chant, to a secular poem, or vulgar song and frequently ended being being the bottom voice. In cyclic masses, a single cantus firmus was used in each movement to give overall unity to the work.

With time various ways of adorning, devloping and altering the use of cantus firmus appeared, including mixing between voices, and interpolating other material, until, as a compositional tool , it ceased to be essential.

Typically the cantus firmus was written using a c clef, and this is, of course, suggested. This will also help keep an idea of vocal range in mind.

For these exercises you should use from eight to thirteen notes of the same value, just to get a feel for the melodic shape. This is the approach recommended in Gradus ad Parnassum, but ultimately when you write this music as your own composition, you will rarely be in such a situation.

There are a number of rules governing melody structure which can be learned here in a monophonic setting. Indeed, writing one's own cantus firmus is the best way to get a feel for the shape of the melodic style.

The rules are thus:

  • Begin and end on the final of the mode.
  • The penultimate note should go to the final in a stepwise manner i.e. from one note above or below the final. If approaching from below the leading note should be raised (except in the phrygian mode)
  • Keep the range within an octave. You can even limit yourself to a fifth or a sixth.
  • Use only diatonic notes - no chromaticism (do not alter a note using a sharp or a flat, or a natural)
  • Allow stepwise motion to predominate
  • Try to change direction of the line frequently to make it attractive and varied. ie change form climbing to falling notes very often.
  • If a leap is larger than a third, follow it with contrary motion, preferably stepwise. 
  • Do not follow  a leap with another one, especially two consecutive thirds.
  • These  melodic intervals may be used: major and minor 2nds, major and minor 3rds, perfect 4ths, perfect 5ths, minor 6ths (ascending only), and perfect octaves.
  • There should be a climax on a high note consonant with the final. This should only be sounded once.
  • Avoid tritones, and outlining tritones.
  • Avoid repeating groups of notes and sequences
These are the basic rules of melody writing appropriate to the style. You should try to write as many short melodies as you can using these rules before proceeding to the next step,  first species.



Counterpoint Index
Modes
Cantus Firmus
1st Species
2nd Species
3rd Species
4th Species
5th Species
Examples

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