Which of the following best defines 'melody'?

A melody is essentially defined as a series of musical notes that are perceived as a single entity. This definition captures the essence of melody as it relates to how listeners experience music. When a sequence of notes is arranged in a coherent and memorable way, it can evoke emotions, tell stories, or convey themes within a piece. Melodies typically have a distinct contour, rhythm, and pitch progression, allowing them to stand out and be recognizable, differentiating them from other musical elements.

In contrast, the other options refer to different facets of music. The harmonic support of a musical piece pertains to chords and the vertical aspect of music, which complements but does not define melody. The rhythmical structure involves the timing and patterns of notes, but does not inherently describe a melody. Finally, dynamic changes relate to the loudness or softness of music rather than the sequence of notes that create a melody. Each of these elements plays an important role in music, but they do not encapsulate the definition of melody itself as succinctly as the correct choice does.