How do simple-strophic, modified-strophic, and through-composed song settings differ?

In the context of vocal music, composers use three primary methods to set strophic poetry, distinguished by how the music relates to the text of each stanza.1

• Simple-strophic: This setting uses a single piece of music that is repeated for every stanza of the poem. It is most effective when the entire poem maintains a central mood or when the composer intends to create a neutral setting that avoids detailed text illustration.1
• Modified-strophic: This approach retains the same basic musical framework for each stanza but introduces changing details in the vocal line or accompaniment to better reflect the progression of the text.1
• Through-composed: In this method, the composer provides a different musical plan for each new stanza. While this does not necessarily mean every musical idea must be entirely new, the defining characteristic is the lack of structural correspondence between the stanzas of the text and the sections of the music.12

The modified-strophic and through-composed methods are generally more successful for poems that feature irregular prosodic patterns, progress toward a dramatic climax, or contain widely differing moods across stanzas.1