A serious and somber mood is not conveyed by a rhythm and rhyme scheme that would be found in the work of Dr. Seuss. When you are writing, think: how does the rhythm and rhyme affect the mood? Rhymed couplets often lighten a poem because adjacent rhyme can be difficult to pull off seriously, especially for a less-experienced poet. Another mood lightening device is trinary rhythms: dactyl, amphibrachic, and anapest for instance. Binary meters, like iambic and trochaic, will give a more serious mood, just as rhyme that is separated more and in intricate patterns can help convey more seriousness. Longer lines also help separate rhymes. Repetition, such as is seen in the villanelle, will intensify the emotion of the poem or make it comic, depending on how deftly the repetition is handled.