Contrary motion
Two voices move in opposite directions.
What it means
Contrary motion is the case in which two voices move in opposite directions: while one voice goes up, the other goes down. It is one of the four kinds of motion of two voices, alongside parallel, oblique, and similar motion.
Musical use
In part-writing, contrary motion counts as a particularly favorable kind of voice leading, because it stresses the independence of the voices and avoids forbidden parallels. It is preferred especially between melody and bass, for instance when closing a cadence, where upper voice and bass strive against each other toward the tonic. It is also used artfully in the fugue and canon through the inversion of the theme.
Contrary motion should be distinguished from parallel motion, in which both voices go in the same direction at the same distance, and from similar motion, in which they progress in the same direction but at a changing distance. In oblique motion one voice stays put while the other moves.
Performance practice
In ensemble playing, listen for the contrary motion: a balance between rising and falling voice makes the texture sound open and transparent. Shape both voices with equal weight so that their movements support each other.