Sonata Form is a musical structure which underpins the vast majority of 1st movements in symphonies, concertos, chamber and solo works of the 18th and 19th centuries. It can also appear in other movements, most often in the final movement of a work or even in the slow movement (usually the 2nd movement).
Sonata form (not to be confused with 'Sonata' - as in Sonata for violin and piano) is not a very complex structure and once one gets the idea, it is easy to understand.
Its development as a form / structure evolved from the compositional need to present and then develop musical ideas such as melodies and themes - 'musical hooks' in modern parlance.
A composer who has a melody or theme needs firstly to present it in a way that is memorable - ie: the listener, after hearing it will be able to recognise it when it appears subsequently and also appreciate how the composer develops or modifies it later on in the movement.
Bear in mind that only in the 20th century did we have access to recorded music allowing us to listen repeatedly to the same piece of music whenever we chose to do so. A music lover in the 19th century would be fortunate to hear a Beethoven symphony or Mozart concerto live more than once - consequently, listening and taking in the musical themes and recognising the structural pillars upon which the piece was built during the performance was really important.
Below is a description of the Sonata Form structure, but first - a health warning: For every Rule there are many exceptions!
|1st theme - Bridge - 2nd theme - Bridge||In this section the composer develops the themes and ideas presented in the Exposition||A more or less repeat of the exposition|
|The Exposition is repeated (played twice)||The Development and Recapitulation are played straight through, without repeats|
Most Exposition sections in Sonata Form have two themes - the first is usually quite assertive, whereas the second is usually more gentle in nature. Ying and Yang if you want.
There are however quite a few instances of mono-thematic expositions - ie: a single theme rather than two, (Mozart's Haffner Symphony no 35 is a good example) and some that have three themes.
The standard formula is:
First theme is presented in the home key (doesn't matter if you don't know what this is)
Next there is a bridge section which quite often uses bits of material from the first theme. The function of the bridge is to take us from the environment of the assertive first theme to that of the more gentle second theme.
Second theme is presented (usually in the key of the dominant - doesn't matter if you don't know what this is)
A second bridge section which takes us to the end of the exposition.
At this point the exposition is either repeated (so that you as a listener have a second chance to memorise the thematic material) or leads straight into the development section
One could easily write a book on this bit, and many have!
On the one hand it is quite simple - the composer takes the thematic material and transforms it, develops it and illuminates it with different lights and shades.
On the other hand, there are a myriad variations on how one goes about it. Haydn and Mozart development sections are very uncomplicated mostly - the different themes appear almost verbatim, perhaps in conjunction with other ideas or orchestrations or harmonic environments. Beethoven on the other hand forensically dissects his themes into little bits,leaving no stone unturned.
Once some or all of the material has undergone this process we come to the final section, the recapitulation
The recapitulation is basically a repeat of the exposition. There are differences which are largely driven by the need to finish the movement in the home key. Consequently there are certain harmonic movements which occur in the recapitulation which are not present in the exposition.
Why bother having a recapitulation at all?
It is like a summing up of a debate. In the Exposition you lay out the arguments, in the development you pick them apart, and in the recapitulation you get to hear them in a new light, having been through the process of the first two sections.
Once you have the basic structure of Exposition - Development - Recapitulation in your mind, it is just a question of practice - deep listening in a disturbance free environment is recommended.
Bear in mind the above mentioned Health Warning - there are few examples of musical works that follow the above formula exactly.However the basic principals of presenting thematic materials and developing them will always be there.