Sonnet 30 up of fourteen lines in three quatrains and a couplet, rhyming "abab cdcd efef gg". While using the rhyming and metrical structure of the 'English' or 'Surreyan' sonnet, Shakespeare often also reflected the rhetorical form of the Italian form also known as the Petrarchan sonnet. It divides the sonnet into two parts: the "octet" (the first eight lines) usually states and develops the subject, while the "sestet" (the last six lines) winds up to a climax. Thus a change in emphasis, known as the "volta", occurs between the end of the eighth and the beginning of the ninth lines —
Sonnet introduced, such as CDCDCD. Petrarch typically used an ABBA ABBA pattern for the octave, followed by either CDE CDE or CDC CDC rhymes in the sestet. The symmetries (ABBA vs. CDC) of these rhyme schemes have also been rendered in musical structure in the late 20th century composition "Scrivo in Vento" by Elliott Carter, inspired by Petrarch's Sonnet 212, "Beato in Sogno".) In English, both the English or Shakespearean sonnet, and the Italian Petrarchan sonnet are traditionally written in iambic pentameter. The first known sonnets in English, written by Sir Thomas Wyatt and Henry Howard, Earl of Surrey, used the