Related
Modulation is moving the tonal centre. Its difference from tonicization is not the technique but duration and depth:
| Tonicization | Modulation | |
|---|---|---|
| How long it lasts | a few chords | a whole passage |
| Does it establish a new centre? | borrows one, then returns | yes, it establishes one |
| Effect | a change of colour | a change of structure |
Close and distant keys
The distance between keys is measured most clearly on the circle of fifths:
| Relation | Key signature difference | Shared notes | Difficulty |
|---|---|---|---|
| close | one sharp or flat apart | six notes in common | smooth |
| moderately distant | two or three apart | four or five in common | needs preparation |
| distant | further apart | few | needs a pivot or an enharmonic device |
The reason close keys are smooth is plain: they share many notes, so no accidentals are needed to move across. "Relative major and minor" (C major and A minor) are the closest relation of all — they share one signature.
Three common devices
One: common chord (smoothest). Use a chord that exists in both keys as a bridge: first hear it as a degree of the old key, then reinterpret it as a degree of the new one.
Two: secondary dominant. Place a dominant chord of the target key in front of it, announcing the new centre (see secondary dominant).
Three: enharmonic reinterpretation (most abrupt). The same note or chord, respelled, belongs to another key — symmetrical structures such as the diminished seventh or augmented triad turn with a change of interpretation (see enharmonic).
What modulation does structurally
Modulation is not merely "changing key"; it is the main way form is divided:
- the development section of sonata form is little more than continuous modulation;
- the middle section of a ternary form typically uses a contrasting key;
- variation sets often change key between variations for freshness.
In other words: the tonal plan is the map of the structure.
Diagram: distances on the circle
Listen: two kinds of transition
Use the circle-of-fifths component to click neighbouring and non-neighbouring keys, comparing "one step away" with "the long way round".
Common misconceptions
- "Modulation and tonicization are the same thing." Tonicization borrows and leaves; modulation establishes a new centre. The difference is duration and depth, not technique.
- "Modulation requires accidentals." Close-key modulations often use none at all, relying on common chords.
- "A relative minor is the same key." Same signature, different centre (C and A are two centres), so two keys.
- "The more abrupt the modulation the better." Abruptness is a deliberate effect (enharmonic rewriting). Usually the composer prepares the listener.
:::
Listen in the library
All tracks from midicn-lib — inline badge is the license tier (C1 commercial / C2 non-commercial / C3 study only).
Sources
- 转调指调性中心的转移；近关系调为相差一个升降号的调，属和声学通则
- 共同和弦、副属和弦、等音重解是常用转调手段，为通行和声学表述
Used for fact-checking only; all prose is original.