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Fourth species changes tack: instead of adding notes, it changes where they sit.
The counterpoint enters half a step late on each note, so it is still holding the previous pitch on the strong beat — that is a suspension.
The three stages of a suspension
A suspension is not "a note that failed to move". It has three strict stages:
| Stage | State | Requirement |
|---|---|---|
| preparation | the note was consonant in the previous chord | it must have been established before it can be held |
| suspension | the chord changes and the note stays, becoming dissonant | the tension is created here |
| resolution | it moves down by step (usually) to a new chord tone | the dissonance is released |
All three are required. The first especially: without preparation a suspension simply sounds like a wrong note, not like postponed tension.
Why it deserves a species of its own
Because it reveals something fundamental in harmony:
Dissonance can be planned.
In second and third species the dissonances are passing (quickly passed over). A suspension is structural — it occupies a strong beat, has an explicit preparation and resolution, and is deliberate tension.
The suspended chord (sus4 / sus2) is this device harmonised: compress "suspension and its resolution" into a single chord and you get a chord that hangs unresolved.
The difficulty: displacement changes every vertical relation
What makes syncopated counterpoint hard is that every vertical relation is offset.
| Moment | Relation to the cantus firmus |
|---|---|
| the suspension lands on the strong beat | it forms a dissonance with the cantus (as intended) |
| after resolution | consonant again |
So what must be checked is not "consonant at every moment" but "is each dissonant moment precisely a suspension about to resolve?" That shifts judgement from result to process — which is also what makes it the closest of the species to real harmonic writing (see treating non-chord tones).
How it differs from second species (easily confused)
| Second species | Fourth species | |
|---|---|---|
| Method of displacement | inserts extra notes | inserts nothing; only shifts notes later |
| Where dissonance lands | weak beat | strong beat — the key difference |
| Nature of the dissonance | passing | structural suspension |
In one line: second species displaces in order to fill; fourth species displaces in order to delay.
Diagram: preparation, suspension, resolution
Listen: postponed consonance
Fourth species is a two-voice exercise and cannot be played here. Use interval to hear the moment the suspension forms: a third (consonant) becomes a fourth (dissonant) and returns to a third — exactly the vertical sound of prepare-suspend-resolve.
Common misconceptions
- "A suspension is just a note that did not change." It must pass through **preparation, suspension and
- "A suspension always resolves downward." Almost always; upward resolutions exist but are rare and need
- "It is second species by another name." The decisive difference is that the dissonance lands on a **strong
- "The suspended chord has nothing to do with suspensions." It is the suspension harmonised: preparation,
resolution**. Without preparation it is merely a wrong note.
special handling.
beat and is structural**, not passing.
suspension and resolution compressed into one chord. :::
Listen in the library
All tracks from midicn-lib — inline badge is the license tier (C1 commercial / C2 non-commercial / C3 study only).
Sources
- 第四类对位（切分对位）以延留音为核心：须经"准备—挂留—解决"三步，属对位学通则
- 挂留和弦（sus2/sus4）即来源于延留音的和声化，为通行和声学表述
Used for fact-checking only; all prose is original.