String Quartets

Since the time of Joseph Haydn in the eighteenth century, the main form of a string quartet has been as follows:
 
1st movement: The first movement is in a Sonata Form, played at a quick spirited pace, most often Allegro tempo. It at least starts in the tonic key, which is the main key of the work, and presents a theme or main melody, which may then be repeated in a variety of different keys.

2nd movement: The second movement is a slower and more songlike piece in an aria form, which contains three central sections: an introduction, a contrasting section in the subdominant key, followed by a reprise of the first section.

3rd movement: The third movement of a string quartet's third movement was based on the court dance music of the eighteenth century. The most popular of these forms is a  minuet and trio, although some composers, such as Beethoven, sometimes substituted scherzos and other dance forms. This movement is lively, and almost always in triple meter time, and played in the tonic key.