“Tonight I Can Write the Saddest Lines” is a free-verse poem, which means it does not have a predictable, traditional rhyme scheme or pattern. Free-verse poetry became increasingly popular in the 20th century as poets abandoned rigid rules of meter and rhyme and wrote poetry that mimicked the speech of everyday people. Though “Tonight I Can Write the Saddest Lines” does not employ a conventional poetry form, it relies heavily on repetition to mimic the structure of a song. The speaker repeats “I can write the saddest lines” and other words and phrases. This helps create a coherent sense of the poem, the way a song creates a coherent rhythm and structure by using repeated lines and refrains. Yet, unlike a song, the repeated lines do not follow a rigid pattern but mimic the way an obsessive person thinks the same thought over and over, with small variations that do not necessarily adhere to a set of rules.

Synecdoche is a literary device wherein an author uses part of a thing to represent the whole. Pablo Neruda writes “My sight tries to find her as though to bring her closer.