Related
Tonal music has seven degrees, but remembering three beats remembering seven, because they do only three jobs:
| Function | Symbol | Degrees (major) | Role |
|---|---|---|---|
| tonic | T | I, VI, III | stable, the place to land |
| subdominant | S | IV, II | leaves the tonic, pushes toward the dominant |
| dominant | D | V, VII | maximum tension, demands a return |
That is the functional circle: T → S → D → T. The skeleton of most classical works fits on that chain.
Why the reduction works
Because some degrees share critical notes:
| Degree | Shares with | Effect |
|---|---|---|
| VI and I | the third and fifth | VI can substitute for I |
| II and IV | the root and third | II can substitute for IV |
| VII and V | the third and fifth (within V7) | VII carries dominant function |
So the "seven degrees" are really several expressions of three functions. It is why analysis often writes only T / S / D — it labels the job, not the number.
Normal and abnormal successions
| Succession | Status | Note |
|---|---|---|
| T → S → D → T | standard | the "main road" of tonal music |
| T → D → T | very common | the subdominant skipped; a more direct close |
| D → S | retrogression | the dominant moves back to the subdominant; sounds like walking backwards |
| S → T (plagal) | common | a gentler close — see [[concept:cadence |
Retrogression is one of the few outright taboos in the system: the dominant is the point of maximum tension, so returning to the subdominant withdraws that tension and leaves the music sounding slack.
Relation to minor
Functional relations hold exactly the same way in minor; the dominant simply requires a raised seventh to produce a major triad (see harmonic minor). So accidentals in minor-key music are not surprises — they are what the function demands.
Diagram: the functional circle
Listen: functional progressions
Use the progression player for T → S → D → T (the standard route) and T → D → T (subdominant skipped). Both close successfully; they differ in how far they travel.
Common misconceptions
- "Function labels are just aliases for degree numbers." They label the job. When a VI acts as a tonic, writing T says more than writing VI.
- "Retrogression is forbidden." Strongly avoided, not forbidden. From the Romantics onward it is used deliberately, for slackening.
- "Minor keys work differently." Exactly the same, except the dominant requires a raised seventh.
- "Function applies only to classical music." The common pop loop (I–V–vi–IV) is just as analysable in functional terms.
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Listen in the library
All tracks from midicn-lib — inline badge is the license tier (C1 commercial / C2 non-commercial / C3 study only).
Sources
- 和声功能把级数归纳为主（T）· 下属（S）· 属（D）三组，属和声学通则
- 功能进行的常见序列（T–S–D–T 与 T–D–T 等）与替代关系为通行表述
Used for fact-checking only; all prose is original.