As I understand cantus firmi means that fixed songs and it is used in counterpoint melodies but I could not understand why is it called cantus firmi and its function. Does anybody know why is it called fixed songs but it is not fixed at all and its funcion?
But how does one determine which one is c.f?
Edit: I read that it is used for music education but still could not understand its function at all!
Edit2: Found some information here
The following characteristics 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 (Fux’s F-major cantus is an exception, where the back-to-back descending leaps outline a consonant triad.)
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
Cantus firmus composition gives us the opportunity to engage the following fundamental musical traits:
independence and integrity or melodic lines
motion (towards a goal)