Part-Writing: Parallel Fifths Hidden by a Suspension
A student submits a four-voice exercise in C major. The progression is I–V–vi–IV–V–I. In the V–vi motion, the student writes: bass G→A, tenor D→E, alto B→C, soprano G→A. The student then adds a suspension in the vi chord, holding the soprano's A over from the V and resolving it to G, and claims this "fixes" any parallels because the soprano is a suspension. The instructor marks parallel fifths between bass and tenor (G–D to A–E) and parallel octaves between bass and soprano (G–G to A–A, before the suspension resolves). The student argues the suspension makes the soprano acceptable.
1. Verify the instructor's claims about parallel fifths and octaves, and explain whether the suspension excuses the soprano's parallel octave.
Read the worked answer
Check each voice pair from V (G–B–D with soprano G) to vi (A–C–E with soprano A):
- Bass–tenor: G–D (a fifth) → A–E (a fifth). Both voices move up by step, and the interval remains a perfect fifth. That is parallel fifths - forbidden in strict part-writing. The instructor is correct.
- Bass–soprano: G–G (an octave) → A–A (an octave). Both move up by step, interval remains a perfect octave. That is parallel octaves. The instructor is correct.
- Alto B→C and tenor D→E against bass G→A: B–G is a third, C–A is a third; fine.
Does the suspension excuse the soprano? No. A suspension delays the resolution of a dissonance; it does not license parallel perfect consonances. The parallel octave occurs between the bass G and the soprano G moving to bass A and soprano A - the soprano's A is the preparation of the suspension, and the motion into it is still a parallel octave. A suspension on the resolution (A→G) would change the soprano's arrival, but the forbidden motion G–G → A–A has already occurred at the attack of the vi chord. The suspension does not retroactively fix the voice leading; it must be prevented at the point of motion.
2. Revise the V–vi motion to eliminate the parallels while keeping the bass G→A and the soprano's suspension figure.
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Constraints: bass must move G→A (the defining deceptive motion), and the soprano should retain a suspension figure (A held over vi, resolving to G). The problem voices are the tenor (D→E creating fifths with bass) and the soprano doubling the bass at the octave.
A clean revision:
- Bass: G → A.
- Soprano: G → A (suspension preparation) → G (resolution). Keep it, but fix the doubling below.
- Alto: B → C (third above bass, fine) - or move B → A to avoid doubling.
- Tenor: D → C (not E). This avoids the fifth with the bass: G–D (fifth) → A–C (third). No parallel fifth.
But now check the soprano octave: bass A with soprano A is still an octave, and the previous bass G with soprano G was an octave - the parallel remains. To break it, the soprano must not arrive on A at the same time as the bass arrives on A. Options:
- Delay the soprano: soprano holds G into the vi chord as a 7th above the bass A (a G over A is a seventh), then resolves down to F♯ or up - but that changes the suspension figure.
- Change the soprano's approach: have the soprano move G → B (third of vi) instead of G → A, and place the suspension in an inner voice. Then bass A with soprano B is a third, not an octave; no parallel octave.
- Use contrary motion: if the soprano must land on A, have the bass approach from a different note (e.g., V in inversion) so the octave is not approached in similar motion.
The most idiomatic fix: soprano G → B (or G → E), tenor D → C, alto B → A, bass G → A, giving vi as A–C–E with the third doubled or root doubled appropriately. If the suspension must be in the soprano, then the bass should not also move G→A in parallel octaves with it; instead use a first-inversion dominant or a different voicing so the suspension is prepared without the parallel.
3. The student claims the suspension "fixes" the parallels. Explain the general principle about non-chord tones and parallel perfect intervals that the student is missing.
Read the worked answer
The principle: non-chord tones and suspensions operate on the surface; they do not erase the underlying voice-leading motion between chord tones. Parallel perfect fifths and octaves are judged between the structural voices at the points where chord tones sound. A suspension delays a resolution, but the preparation and the attack of the chord still involve chord tones moving in parallel perfect consonances.
More precisely:
- A suspension is a dissonant interval (a second, fourth, seventh, or ninth above the bass) that resolves by step. The parallel-perfect rule concerns perfect consonances (unison, fifth, octave). A suspension is not a perfect consonance, so it cannot be the thing that "cancels" a parallel fifth or octave - those occur between other voices or at other moments.
- If the soprano's A is a suspension, the interval above the bass A is a unison (if soprano A) - that is a perfect interval, and the motion into it from the previous G–G octave is a parallel octave regardless of the later resolution.
- The correct remedy is to change the voicing or doubling so that no two voices move in parallel perfect consonances, not to add a non-chord tone on top.
The student should re-voice the chord (as in the previous task) and then, if desired, add the suspension in a voice where it does not create a parallel perfect interval with the bass.