What term refers to parts that move in opposite directions, such as one ascending while the other descends?

The term that describes parts moving in opposite directions, such as one part ascending while the other descends, is known as contrary motion. This musical concept involves two or more melodic lines or voices moving away from each other, increasing the harmonic richness and creating a sense of counterpoint. Contrary motion is important in various musical styles because it helps to balance the texture and adds interest to the music, making the interaction between parts more dynamic.

In contrast, parallel motion refers to parts moving in the same direction at the same interval, which does not create the same sense of opposition. Contrapuntal motion generally refers to the interplay of independent melodic lines but does not specifically denote the directional movement. Harmonic motion relates to the movement between chords rather than the motion of melodic lines themselves. Thus, the concept of contrary motion directly aligns with the description of moving in opposite directions.