How does sound contribute to a poem?

Answer 1

Human ears find sounds that go with a beat more pleasing, and easier to remember. I poem that has, say, iambic pentameter, is going to be on the reader can enjoy because he knows what to expect from line to line, as far as rhyme schemes go. A poem with no rhyme scheme may be harder to understand. Sometimes it's difficult to figure out which line goes with what.

Answer 2

Think of music, the sound helps set the mood of the song. For example read Bob Dylan's lyrics then listen to the song.
http://www.bobdylan.com/songs/