Rhythm

The surest way to reach the heart [of the reader] is through the ear. The visual images thrown up by a poem are important, but it is more important still to choose and arrange words in a sequence so as virtually to control the intonations and pauses in the reader’s voice. By arrangement and choice of words on the part of the poet, the effects of humor, pathos, hysteria, anger, and in fact, all effects, can be indicated or obtained.
— Robert Frost