The contrapuntal motion of one voice moving while the other voice remains statinoary is called oblique motion.
5-6 technique
the one way to create a consonant step motion : by moving from a fifth to a sixth or a sixth to a fifith. the generic term for such step motion is 5-6 technique.
compound melody
Sometimes these skips and leaps occur several times,creating the effect of splitting a single line into two separate voices, a technique which we call comound melody.