Final answer:
In a melody, 'opposite pairs of motion' describe parts moving in contrasting directions, such as one ascending while the other descends, adding dynamism and tension to the music.
Step-by-step explanation:
The term 'opposite pairs of motion' in a melody refers to instances where parts of the melody move in contrasting directions. Consider, for example, two voices in a musical piece, where one voice ascends the scale while the other descends. This technique can create a sense of tension and release, balance, and interest within the piece. Simple Harmonic Motion provides a physical analogy: the acceleration and therefore the net force is proportional to and acts in the opposite direction of displacement. Similarly, in music, beats created when two notes of slightly different frequencies are played together can involve alternating between constructive and destructive interference, producing a warbling effect due to the waves moving in opposite phases.