How does sonata form work?

Sonata form is one of those things that seems rather scary at first, but once you get to grips with it it's actually a lot more simple than you think, and unlocks a whole load of music in one go! So, here goes...

The easiest way to think about sonata form is as three separate 'bits', each of which contain a pretty much the same music, but use it in slightly different ways. These separate bits are:

1) Exposition

2) Development

3) Recapitulation

Now, within each of these there are two lots of musical material, called the 1st subject group and the 2nd subject group. These two strands of music basically make up the entire piece, by being used slightly differently in each of the sections. To understand it, we'll go through each of the sections in order. Let's start with the exposition:

Exposition

This is the first section of the sonata form. The first music we hear (there might be a short introduction before it, but this is often not the case) is the 1st subject. The 1st subject is just a fancy way of saying '1st tune' - it's just a melody that is heard in various instruments, and makes up the first part of the exposition section. Once the 1st subject is over, it's the turn of the 2nd subject - or, in the simple way of thinking about it, a different tune. Once this has finished, that marks the end of the exposition. So, the exposition can be thought of as:

(introduction) 1st subject...... 2nd subject......

Development

This is the next section of a sonata form and is where things get fun. In this section, the composer will mix both subjects that were heard in the exposition together, playing one off against the other. Both 'tunes' are heard at the same time in a sort of 'two tune blend'...!

Recapitulation

This is the final section of a sonata form, and is pretty similar to the exposition. After the development section has finished, the 1st subject comes back again on its own, before the 2nd subject comes back again in the same way it did in the exposition. The piece may well end with something called a Coda - essentially, this is just an extra little bit stuck onto the end, which is used to bring the piece to a close. So, the recapitulation can be thought of as:

1st subject..... 2nd subject.... Coda.....

Between every section, there is something called a 'bridge' - this is a short passage of music that allows the composer to switch between the section without having to stop and start again (it's very useful if they want to modulate).

So - the structure of a sonata form is:

Exposition

   - (introduction)

   - 1st subject

   - 2nd subject

   - Bridge

Development

   - both 1st and 2nd subjects at the same time

   - Bridge

Recapitulation

   - 1st subject

   - 2nd subject

   - Coda

See, it's simple really! The final thing to consider is the tonal structure of a sonata form (which keys each of the sections is in), but that's another question entirely - for another day...!