Contrapuntal motion

In music theory, contrapuntal motion is the general movement of two melodic lines with respect to each other. In traditional four-part harmony, it is important that lines maintain their independence, an effect which can be achieved by the judicious use of the four types of contrapuntal motion: parallel motion, similar motion, contrary motion, and oblique motion. See also melodic motion.

Parallel motion is motion in the same direction, keeping the same interval between them. For example  Play :

Parallel motion at an interval of a perfect fifth is known as parallel or consecutive fifths, and at an interval of an octave is known as parallel or consecutive octaves. These motions are generally avoided in traditional counterpoint because they offer the lines so little independence from each other.

Similar motion is motion in the same direction, but with the interval between them changing. In other words, both lines move up, or both lines move down, but the interval between them is different in the first chord and the second chord. For example  Play :

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