Harmony contributes to the effect of motion in music. Since harmony is derived from scale pitches, harmony automatically assumes the gravitational properties that scales display. The gravitational attraction of scale pitches impart goal-oriented motion to the effect of harmonic progressions that are designed with this gravitational effect in mind. Chords that move by root movement up an interval of a fourth, down a fifth, down a third or up a second, give a strong sense of goal oriented motion to passages of music. Since rhythm is also an integral part of harmonic accompaniment, harmonic progressions contribute a strong and sustained sense of movement to music.
Harmony contributes to the structural design of music.
The arrangement of melodic material lends itself to hierarchical design more noticeably than does harmony. This is because repetition of patterned material is more obvious in melody than it is in harmony. In this sense harmony does support the structural design of melody and overall musical material generally. However, harmony is the material composers most often vary when harmony accompanies repetitive portions of melody.