Sonata form is one of the most influential ideas in the history of Western classical music. Since the establishment of the practice by composers like C.P.E. Bach, Haydn, Mozart, Beethoven, and Schubert and the codification of this practice into teaching and theory, the practice of writing works in sonata form has changed considerably. Late Baroque era (ca 1710 – ca 1750) Properly speaking, sonata form did not exist in the Baroque period; however, the forms which led to the standard definition did. In fact, there is a greater variety of harmonic patterns in Baroque works called sonatas than in the Classical period. The sonatas of Domenico Scarlatti provide examples of the range of relationships of theme and harmony possible in the 1730s and 1740s. Sonatas were at first written mainly for the violin. Over time, a formal type evolved, predominating until the late 18th century. This type reached its peak in the sonatas of J.S. Bach, Handel, and Tartini, who followed older Italian models and employed a type attributable to masters such as Corelli and Vivaldi (Musical Form, Leichtentritt, Hugo, p. 122). By the 1730s and 1740s, the direction of instrumental works, often considered less important than vocal music, tended towards an overall two-part layout: the binary form. But a section of contrasting material which served as a bridge between them also came to be included. Classical era (ca 1750 – ca 1825) The older Italian sonata form differs considerably from the later sonata in the works of the Viennese Classical masters. Between the two main types, the older Italian and the more "modern" Viennese sonata, various transitional types are manifest in the middle of the 18th century, in the works of the Mannheim composers, Johann Stamitz, Franz Xaver Richter, C.P.E. Bach, and many others. The crucial elements that led to the sonata form were the weakening of the difference between binary and ternary form; the shift of texture away from full polyphony (many voices in imitation) to homophony (a single dominant voice and supporting harmony); and the increasing reliance on juxtaposing different keys and textures. As different key relationships took on a more and more specific meaning, the schematics of works altered. Devices such as the false reprise fell out of favor, while other patterns grew in importance. Quite probably the most influential composer on the early development of sonata form was C.P.E. Bach, a son of J.S. Bach.