Sonata-allegro is a form that emerged during the period known as the “Age of Enlightenment” due to the renewed interest in classical knowledge and philosophy as a result of the new science from the Baroque Era. It was used by many writers, for example, Franz Joseph Haydn and Wolfgang Amadeus Mozart.
Sonata Allegro form developed in the Classical form period. It is a new formal form based upon structural balance. The three structural components are, Exposition, which is at the beginning and it “exposes” or presents the Primary, Transitional, Secondary and Closing Themes. The Primary theme, also known as the 1st theme, is in the tonic, the transition section or theme is modulatory to the Secondary theme (2nd theme) which is in a contrasting key (dominant or relative major). The primary and secondary themes also contrast each other in melody, dynamics, instrumentation and character. Finally, there is the closing section or theme. Development Section which takes a new look at the opening themes. This is the very creative section that allows the composer to rework or play with his themes occasionally adding new materials, fragmentations of themes, modulations, contrapuntal ideas, sequences and combinations of themes. After having played with his themes the Recapitulation “recaps” or reviews the material of the exposition but without modulation away from the tonic key.
This form is often used for the 1st and 4th movements of a Symphony. Movement 2 is often a theme and variations or rondo (usually some sort of slower movement) and movement 3 is usually a dance such as the Minuet and Trio or Scherzo.
Sonata-allegro was the most important form to develop during this period, since it come and took place of Baroque Ritornello form to become the most important form in History. This is because it emphasized more on a formal structure that was balanced and clear as compared to the heavy and a more pedantic Baroque Ritornello. Sonata-allegro is still used today worldwide.
This form is often considered dramatic and rewarding because it has a creative section which allows the composer to rework or play with the theme occasionally in order to add something new to the form. This is rewarding because it helps the composer to improve the quality and clarity of his or her composition.