Parallel fifths
Parallel fifths arise when two voices a perfect fifth apart move one after the other in the same direction. In strict harmony teaching they count as a mistake, because the two voices fuse into one sound. In rock music and Impressionism, by contrast, they are a deliberate stylistic device.
- Meaning
- fifth → fifth, both voices in the same direction
- Also forbidden
- parallel octaves
- Reason
- voices lose their independence
- Remedy
- contrary motion or another target note
- Used on purpose
- power chords, organum, Impressionism
The sound of the fifth
The perfect fifth has the simplest ratio after the octave: 3 to 2. That is why its two notes fuse so strongly that the ear hears them almost as one sound. The article Why the fifth sounds hollow describes why a fifth can sound empty despite its almost perfect purity. This very fusion is the problem: two voices that run in parallel in fifths give up their independence.
The mistake: fifth, fifth
The fifth C–G moves to D–A: both voices rise a whole tone, the distance stays a perfect fifth. Twice in a row the distance sounds the same, and the voices seem like a single, thick line.
The remedy: contrary motion
The lower voice again goes to D, the upper falls to F. The fifth becomes a minor third, and both voices stay recognisable as lines of their own.
The intention: power chords
Two fifths that run in parallel in exactly the same way: A5 to D5. In rock guitar that is wanted, for the fifth sounds clear and strong when distorted.
Why harmony teaching forbids them
Polyphonic music depends on each voice staying audible as a line of its own. Parallel fifths and octaves wipe out that impression. Even the counterpoint treatises of the late Middle Ages and the Renaissance avoid them, and every harmony teacher marks them. The ban concerns two successive perfect fifths between the same two voices in similar motion. Contrary motion often serves as a remedy, as in the second example.
Not every fifth is a violation. A single fifth is unproblematic. Two fifths in contrary motion (antiparallel fifths) are treated differently by textbooks: some allow them, strict teachings restrict them. What is forbidden is the sequence of two perfect fifths between the same voices in the same direction. Strict textbooks also know hidden fifths, in which two voices approach a fifth in the same direction. They are less strictly regulated and are judged differently depending on the teaching.
When fifths are wanted
The ban applies to classical polyphonic writing. Medieval organum, early polyphony, led a second voice in parallel fifths or fourths with the melody. Claude Debussy and other composers of Impressionism brought parallel fifths back, for their open sound. And in rock music power chords consist of root and fifth and are deliberately shifted in parallel, more under Power chord.
Common mistakes
- Taking all fifths as forbidden: only two perfect fifths in a row in similar motion between the same voices.
- Forgetting parallel octaves: the same ban applies to them.
- “Hiding” the parallel with a rest: the ear hears it anyway.
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Related terms
Parallel motionContrary motionSimilar motionPerfect fifthFifthPower chordOctaveParallel thirdsCounterpoint
Editor: Maik Krohm · reviewed on 3 October 2026
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