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Cantus firmus (often abbreviated c.f.) is one instruction: start with a given melody, then write the other voices around it.
It deserves its own entry because it halves the difficulty of polyphonic writing:
| What is removed | What is gained |
|---|---|
| no need to invent every voice at once | you can focus on one note of one line at a time |
| the frame is already fixed | vertical relations have a definite reference |
That is why all five species are built on a cantus firmus (see first species): it separates composing from handling — you need only decide how to write around it, not what it should be.
Its two historical identities
| Identity | Explanation |
|---|---|
| compositional device | the medieval and Renaissance cantus-firmus Mass: a whole Mass built on one chant melody, each movement using it (or a transformation of it) |
| training tool | the given melody in counterpoint exercises — still today |
The second survives in the classroom; the first left behind an important idea: an existing melody can serve as the foundation of an entire work. That idea later grew into variation form, ground bass and the whole family of "fixed material" writing.
Where the cantus firmus may sit
Early practice placed it in the lowest voice (the word "tenor" literally means "holder"). Later writing freed it to any position:
| Position | Effect |
|---|---|
| bass | most traditional; the harmonic frame is clearest |
| top | the cantus becomes the melodic protagonist and the others accompany |
| inner voice | the most concealed use — the cantus becomes a hidden thread |
The last is worth noting: a cantus concealed in an inner voice is aimed at listeners who know the inside story — such hidden structures abound in Renaissance and Baroque music.
How it differs from a ground bass (easily confused)
| Cantus firmus | Ground bass | |
|---|---|---|
| What is fixed | a melody (short or long, in any voice) | a bass line (usually short, repeating) |
| Does it repeat? | not necessarily | yes, in a loop |
| The other voices | usually set once per note | a new variation written for each cycle |
In one line: a cantus firmus is a foundation; a ground bass is a foundation on repeat.
Diagram: one line fixed, the rest growing around it
Listen: writing over a fixed frame
Use progression on a functional progression and imagine the position of "the frame is given": bass and harmony are fixed; what you decide is the writing above. That is precisely the situation cantus-firmus training creates.
Common misconceptions
- "A cantus firmus is only an exercise." It was also a central compositional device (the cantus-firmus Mass)
- "The cantus firmus must be in the bass." That was early practice; later it may sit anywhere, and concealed in
- "Cantus firmus and ground bass are the same thing." The first is a melody (not necessarily repeating); the
- "Using a cantus firmus is not composing." Writing around it is the composing. Many of history's most complex
and gave rise to variation form, ground bass and related practices.
an inner voice it becomes a hidden structure.
second is a repeating bass line.
polyphonic works are built on someone else's melody. :::
Listen in the library
All tracks from midicn-lib — inline badge is the license tier (C1 commercial / C2 non-commercial / C3 study only).
Sources
- 固定旋律指预先给定、作为写作骨架的旋律；中世纪以来用于定旋律弥撒与对位训练，为音乐史与对位学通行记载
- 固定旋律在各声部间的位置可移动（低音 / 上方 / 内声部），为通行表述
Used for fact-checking only; all prose is original.