Related
The division of labour matches fugue form:
T6's "canon" covers the writing (one melody strictly followed by another voice); this entry covers the structure — what the sections consist of when that writing is organised into a piece.
Three structural shapes
| Shape | Explanation | Example |
|---|---|---|
| complete canon | the whole piece is one canon (followed from start to finish) | canon pieces and rounds |
| canon sections | the piece has several sections, some of them canons | see the Goldberg Variations below |
| canonic transition | canonic writing used only at a join between sections | countless Classical transitions |
⭐ An outstanding structural example: the Goldberg Variations
Bach's organisation deserves separate mention, because it turns "canon" into a structural principle:
| Fact | Structural meaning |
|---|---|
| every third variation is explicitly marked Canon | the canon becomes a periodic anchor, not an occasional device |
| the entry interval increases each time: unison → second → third → … → ninth | the rule itself changes — this is the organising axis of the whole work |
| the remaining variations are dances, toccatas, fugal pieces | they supply contrast, making the canons' returns weightier |
Note the second row: what varies is not only the music but the rule. That differs from variation form's "change the surface, keep the frame" — here the manner of following changes, so frame and rule are both transformed.
The comparison with fugue form
Both are polyphonic, but what holds the structure up differs:
| Canon form | Fugue form | |
|---|---|---|
| What changes | the following rule (spacing, interval, direction, note values) | the key and density of the subject's appearances |
| Free passages | fewer (canon sections are highly strict inside) | yes (episodes are exactly that) |
| Structural markers | often section contrast (canon variations alternating with non-canons) | three-part logic (exposition, middle, final) |
In one line: a fugue is organised by where the subject goes; a canon is organised by how the following rule changes.
Diagram: the rule itself as the structural axis
Listen: one material, different heights
Use interval to hear the relation of the same material entering at different heights (a third, a fifth) — the material is unchanged, the entry interval is not. That is the smallest demonstration of a canon form's "change of rule".
Common misconceptions
- "Canon form means a canon." Related but different levels: a canon is writing, canon form is the
- "Canon form varies too little to sustain length." The Goldberg Variations sustain an entire set through an
- "It is much like fugue form." Different things change: one varies the rule, the other **key and
- "There is no contrast between canon sections." They usually alternate with non-canonic variations (dances,
structural arrangement of a whole piece.
escalating rule — proof that it can carry a rigorous large structure.
density**.
toccatas, fugal pieces) — the alternation itself is the structure. :::
Listen in the library
All tracks from midicn-lib — inline badge is the license tier (C1 commercial / C2 non-commercial / C3 study only).
Sources
- 卡农曲式指以卡农写法组织整曲时的结构安排，与"卡农（写法）"分属不同层面，属曲式分析通则
- 巴赫《哥德堡变奏曲》每三首变奏含一首卡农、进入间隔逐次递增，为音乐史通行记载
Used for fact-checking only; all prose is original.