Counterpoint
Types of Motion in Voice Leading: Parallel, Contrary, Oblique
Parallel, similar, oblique and contrary motion defined between two voices, what each does to their independence, and which one counterpoint prefers.
Parallel motion
Two voices moving in the same direction by the same interval, so the interval between them is preserved. Parallel fifths and octaves are forbidden.
Also called: Parallel voices, Parallel thirds, Parallel sixths
Parallel motion is the movement of two voices in the same direction, keeping the interval between them the same. Parallel thirds and parallel sixths are common in tonal writing, and many melodies are harmonised in thirds. In C major, the pair C and E moving up to D and F♯ keeps a major third between the voices, and both rise by a step. Parallel perfect intervals, meaning fifths and octaves, are a different matter. In common-practice part writing they are avoided, because the two voices lose their independence and fuse into one line. Parallel thirds and sixths carry no such problem, so they are used freely when harmonising a melody.
Related terms
- Parallel fifthsTwo voices that move in the same direction and stay a perfect fifth apart from one chord to the next, a standard fault in part writing.
- Contrary motionTwo voices moving in opposite directions, one rising while the other falls. It keeps the voices independent and avoids parallel perfect intervals.
- Oblique motionOne voice holds or repeats a single note while another moves, so the harmony changes against a fixed pitch. Common in pedal passages.
- Voice leadingHow individual parts move from one chord to the next, favouring stepwise motion and common tones so that each line stays smooth and clear.
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Counterpoint
Parallel Fifths and Octaves: Why the Rule Exists
Parallel fifths and octaves are voices that move together and keep a perfect interval. Here is why strict voice leading forbids them and where the rule bends.