The sonnets of Petrarch and Shakespeare represent, in the history of this major poetic form, the two most significant developments in terms of technical consolidation—by renovating the inherited material—and artistic expressiveness—by covering a wide range of subjects in an equally wide range of tones. Both writers cemented the sonnet's enduring appeal by demonstrating its flexibility and lyrical potency through the exceptional quality of their poems. Sonnet structure The sonnet is a type of poem finding its origins in Italy around 1235 AD. While the early sonneteers experimented with patterns, Francesco Petrarca (anglicised as Petrarch) was one of the first to significantly solidify sonnet structure. The Italian or Petrarchan sonnet consists of two parts; an octave and a sestet. The octave can be broken down into two quatrains; likewise, the sestet is made up of two tercets. The octave presents an idea to be contrasted by the ending sestet. The particular quatrains and tercets are divided by change in rhyme. Petrarch typically used an ABBA ABBA pattern for the octave, followed by either CDE CDE or CDC DCD 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 inspired by Petrarch's Sonnet 212, Beato in Sogno.) The rhyme scheme and structure of Petrarch's sonnets work together to emphasize the idea of the poem: the first quatrain presents the theme and the second expands on it. The repeated rhyme scheme within the octave strengthens the idea. The sestet, with either two or three different rhymes, uses its first tercet to reflect on the theme and the last to conclude. William Shakespeare utilized the sonnet in love poetry of his own, employing the sonnet structure conventionalized by English poets Wyatt and Surrey. This structure, known as the English or Shakespearean sonnet, consists of three quatrains and a concluding couplet. The rhyme scheme is a simple ABAB CDCD EFEF GG format. The effect is “like going for a short drive with a very fast driver: the first lines, even the first quatrain, are in low gear; then the second and third accelerate sharply, and ideas and metaphors flash past; and then there is a sudden throttling-back, and one glides to a stop in the couplet”. Like Petrarch, Shakespeare used structure to explore the multiple facets of a theme in a short piece. Example of Petrarchan