Sonata Form

            Sonata form (also sonata-allegro form or first movement form) is a musical structure 

            consisting of three main sections: an exposition, a development, and a recapitulation. 

            It has been used widely since the middle of the 18th century (the early Classical period). 

            It was more of a general convention to adhere to (and often manipulate) rather than 

            a strict form with rules.

      The Typical First Movement of symphonies, string quartets, 

       sonatas (and more) had three main sections  (the "Sonata Form"):

     1.  Exposition  -  Typically it states the two themes, often in two different keys:

         The first theme (known as das Thema) is in the key of the composition's primary key.  

         The second theme is then introduced, usually in a different key than the first. 

          (in some works the exposition is repeated before going on to the development section) 

     2.  Development  -  Next, the two themes are used in variations to create the real "excitement"
                                      of the movement.  This is where the composer shows off his creativity.

     3.  Recapitulation  -  Then the first two themes are replayed, usually with harmonic
                                         variations to keep them interesting.

           Between Theme 1 and Theme 2 there is usually a modulation bridge, a piece of music 

           usually less than 20 seconds long, that allows the transition from key area 1 of Theme 1 

           to key area 2 of theme 2.  


       Optionally: 

              1.  There could be a coda ("tail") where the composer adds something to rap up the 

                    end of the movement.  Prior to Beethoven, the coda was usually 20 to 40 seconds long.

              2.  The first movement could have a slow introduction before the Exposition began.
                   Beethoven used an introduction in Symphonies 1, 2, 4, and 7.



More on the sonata form:


            While it is typically used in the first movement of multi-movement pieces, it is sometimes 

             used in subsequent movements as well—particularly the final movement. The teaching of 

             sonata form in music theory rests on a standard definition and a series of hypotheses about 

             the underlying reasons for the durability and variety of the form—a definition that arose 

             in the second quarter of the 19th century. There is little disagreement that the form consists 

             of three main sections: an exposition, a development, and a recapitulation; however, beneath 

             this general structure, sonata form is difficult to pin down to a single model.