As we mentioned in the "Symbols, Imagery, Wordplay" section, Teasdale chose Love Songs as the title for her collection containing "Barter." This sense of music is key throughout much of Teasdale's poetry (Get it? Key? As in, let's play it in the key of G? Okay, moving on…). The New York Times Book Review called Teasdale "first, last, and always a singer," and described her 1915 book Rivers to the Sea as, "a little volume of joyous and unstudied song." So, like Shmoop said: with Teasdale, music is key.
Teasdale gives her poems a musical feel by using strong, regular meter (often iambic), coupled with strong end rhyme. The meter gives her verse a very obvious rhythm and the end rhyme ties the lines together in a way that many song lyrics are written. When you read Teasdale's poems aloud, you can really hear and feel the music in the words.
For some other examples of Teasdale's musical verse, take a look at "The Kiss," "The Wind," and "I Might Have Sung of the World."