Rules
- The counterpoint is in half notes tied over the barline: each note enters on a weak beat and is held into the next strong beat.
- On the weak beat the note must be consonant (preparation).
- On the strong beat, when the cantus firmus changes, it may become dissonant (suspension) and must resolve by step downward on the weak beat.
- Good suspensions above the CF: 7–6, 4–3, (9–8 sparingly). Below the CF: 2–3. Avoid chains of 6–5, which lead to fifths.
- If the syncopated note is consonant (e.g. 5–6), no resolution is required.
Cadence example in C major
Cantus firmus: D4 | C4.
Counterpoint above: C5 (prepared earlier, held over D4: a seventh) → B4 (sixth) → C5 (octave above C4).
This is the 7–6–8 cadence: the most classic closing formula.
Why it matters
Suspensions are the main source of “sweet” tension in tonal music: the same idea lives in the sus4 chord that resolves to the third (Gsus4 → G), in pads that hold a note while the harmony changes, and in the inner voices of choirs.
Real-world example
The chains of 7–6 and 4–3 suspensions in Arcangelo Corelli's Trio Sonatas (late 1600s) are the historical model; in pop, every Gsus4 – G before the tonic is a fourth-species suspension that resolves.