Similar Motion
Two voices moving the same way — a common source of parallel fifths and octaves
Related
Similar motion has two voices moving in the same direction: both up or both down. It is perfectly normal in itself; the problem arises when they move the same way and keep the same interval — that becomes parallel fifths or octaves and weakens the independence of the parts.
Its difference from parallel motion is that similar motion looks only at direction, while parallel also requires the interval to stay the same. The usual mistake is to avoid all similar motion — it is the normal case; what to avoid is direct fifths/octaves and parallel fifths/octaves, not similar motion itself.
Read deeper → voice leading
Sources
- 声部进行分类与平行五八度的限制，参 The New Grove Dictionary of Music and Musicians, "Voice leading"；本文为原创表述
Used for fact-checking only; all prose is original.