Sondheim on rhyme

All rhymes, even the farthest afield of the near ones (home/dope), draw attention to the rhymed word; if you don’t want it to be spotlighted, you’d better not rhyme it. A perfect rhyme snaps the word, and with it the thought, vigorously into place, rendering it easily intelligible; a near rhyme blurs it. A word like “together” leads the ear to expect a rhyme like “weather” or “feather.” When the ear hears “forever,” it has to pause a split second to bring the word into focus. Like a note that’s a bit off pitch, a false rhyme doesn’t destroy the meaning, but it weakens it…

Jokes work best with perfect rhymes. Emotional statements are sometimes effective using identities, because the repetition of the sound parallels the intensity of the feeling; it’s a technique particularly favored by Hammerstein (“Younger than springtime am I / Gayer than laughter am I”). I’ve never come across a near rhyme that works better than a perfect rhyme would…

There are reasons not to rhyme, too—not only not to rhyme but to keep the consonant and vowel sounds as different from each other as possible. In fact, songs without rhymes, whose lines end with sounds completely unlike each other, can invigorate the nonrhymed words more than approximate rhymes.

—Stephen Sondheim, Finishing the Hat