How do musical phrases create the structure of a melody?

A melody is defined as an organized succession of musical tones, and its structure is primarily built from phrases—complete musical utterances that roughly correspond to what can be sung or played in a single breath.1

These phrases create structure through their relationships to one another, often utilizing:
* Repetition: The same phrase is repeated to reinforce a theme.1
* Contrast: A completely different phrase is introduced to provide variety.1
* Variation: A phrase is altered while maintaining its recognizable identity.1

Phrases are often grouped into complementary pairs, such as an antecedent and consequent, functioning like a "question and answer" to create a sense of balance. The end of a phrase is marked by a cadence, which acts as a point of articulation or conclusion. Depending on the harmonic or melodic resolution, a cadence can signal a temporary pause or a final ending, helping to organize the melody into larger hierarchical structures like periods or sentences. When no repetitive plan is used, the melody is described as through-composed.12