Composing a cantus firmus

Exercises in strict voice-leading, or species counterpoint, begin with a single, well formed musical line called the cantus firmus (fixed voice, or fixed melody; pl. cantus firmi). Our first exercises in strict voice-leading will be to compose a good cantus firmus.

The first step is to sing and analyze model cantus firmi. A number of them are provided here. (These models will also be used as the starting points for our two-voice exercises.)

From these cantus, notice the following general characteristics, which are typical of all well formed cantus firmi:

• length of about 8–16 notes
• arhythmic (all whole notes; no long or short notes)
• begin and end on do
• approach final tonic by step (usually re–do, sometimes ti–do)
• all note-to-note progressions are melodic consonances
• range (interval between lowest and highest notes) of no more than a tenth, usually less than an octave
• a single climax (high point) that appears only once in the melody
• clear logical connection and smooth shape from beginning to climax to ending
• mostly stepwise motion, but with some leaps (mostly small leaps)
• no repetition of "motives" or "licks"
• any large leaps (fourth or larger) are followed by step in opposite direction
• no more than two leaps in a row; no consecutive leaps in the same direction
• the leading tone progresses to the tonic
• in minor, the leading tone only appears in the penultimate bar; the raised submediant is only used when progressing to that leading tone