<P> The aria evolved typically in one of two forms . Binary form arias were in two sections (A--B); arias in ternary form (A--B--A) were known as da capo arias (literally' from the head', i.e. with the opening section repeated, often in a highly decorated manner). In the da capo aria the' B' episode would typically be in a different key--the dominant or relative major key . Other variants of these forms are found in the French operas of the late 17th century such as those of Jean - Baptiste Lully which dominated the period of the French baroque; vocal solos in his operas (denominated of course by the French term, airs) are frequently in extended binary form (ABB') or sometimes in rondeau form (ABACA), (a shape which is analogous to the instrumental rondo). </P> <P> In the Italian school of composers of the late 17th and early 18th century, the da capo form of aria came gradually to be associated with the ritornello (literally,' little return'), a recurring instrumental episode which was interspersed with the elements of the aria and eventually provided, in early operas, the opportunity for dancing or entries of characters . This version of aria form with ritornelli became a dominant feature of European opera throughout the 18th century . It is thought by some writers to be the origin of the instrumental forms of concerto and sonata form . The ritornelli became essential to the structure of the aria--"while the words determine the character of a melody the ritornello instruments often decided in what terms it shall be presented ." </P> <P> By the early 18th century, composers such as Alessandro Scarlatti had established the aria form, and especially its da capo version with ritornelli, as the key element of opera seria . "It offered balance and continuity, and yet gave scope for contrast . (...) The very regularity of its conventional features enabled deviations from the normal to be exploited with telling effect ." In the early years of the century, arias in the Italian style began to take over in French opera, giving rise eventually to the French genre of ariette, normally in a relatively simple ternary form . </P> <P> Types of operatic aria became known by a variety of terms according to their character--e.g. aria parlante (' speaking - style', narrative in nature), aria di bravura (typically given to a heroine), aria buffa (aria of a comic type, typically given to a bass or bass - baritone), and so on . </P>

The purpose of an aria is primarily to